<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2023 Workiva-->
<!--r:9b587981-7d49-4d79-bd9a-5e53100f802e,g:0ded78a0-ec92-421b-a5e4-045b18119434-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/COVERPAGE" xlink:type="simple" xlink:href="bdn-20230630.xsd#COVERPAGE"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/COVERPAGE" xlink:type="extended" id="i953238e550db4f8896d2b08ed69243fb_COVERPAGE">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_8a3ac1a4-b1bf-4837-ab18-795af1edbca6" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_DocumentType_8a3ac1a4-b1bf-4837-ab18-795af1edbca6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_efb68ba5-b8b3-47a7-a67b-38bd306c14a0" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_DocumentQuarterlyReport_efb68ba5-b8b3-47a7-a67b-38bd306c14a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_4cdad112-3d56-4183-a502-cde9fe46299b" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_DocumentPeriodEndDate_4cdad112-3d56-4183-a502-cde9fe46299b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_3f645c79-b348-40a2-9249-f9e6cfa429ce" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_DocumentTransitionReport_3f645c79-b348-40a2-9249-f9e6cfa429ce" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_5f6382e2-7ec1-48ba-a22c-0f1dd83c5b56" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntityRegistrantName_5f6382e2-7ec1-48ba-a22c-0f1dd83c5b56" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_91636759-0589-4677-ab80-c8ba0482b47f" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntityIncorporationStateCountryCode_91636759-0589-4677-ab80-c8ba0482b47f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_674543d0-715e-4dab-9f62-84c7b0275368" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntityFileNumber_674543d0-715e-4dab-9f62-84c7b0275368" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_d9b6dabe-a1fc-4640-b8cb-181cb437d738" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntityTaxIdentificationNumber_d9b6dabe-a1fc-4640-b8cb-181cb437d738" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_425838a8-cd8a-4b48-a49a-d1fe56868b04" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntityAddressAddressLine1_425838a8-cd8a-4b48-a49a-d1fe56868b04" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_bc5046e1-05a9-4e2d-a8b5-b949288a61f0" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntityAddressAddressLine2_bc5046e1-05a9-4e2d-a8b5-b949288a61f0" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_fdd51e5c-33cc-4ef3-860a-654dca7250c1" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntityAddressCityOrTown_fdd51e5c-33cc-4ef3-860a-654dca7250c1" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_d9583923-5d14-440e-b9e5-2b3b86b610be" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntityAddressStateOrProvince_d9583923-5d14-440e-b9e5-2b3b86b610be" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_6b73a16b-de5a-42b7-96ee-1979da3b401a" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntityAddressPostalZipCode_6b73a16b-de5a-42b7-96ee-1979da3b401a" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_d5877383-bd40-4c35-b820-80d96504c68b" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_CityAreaCode_d5877383-bd40-4c35-b820-80d96504c68b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_ece42b40-c1f4-402d-91e0-551538d3a960" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_LocalPhoneNumber_ece42b40-c1f4-402d-91e0-551538d3a960" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_9edd9a58-26fd-473b-8c91-f8250bdee2bd" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_Security12bTitle_9edd9a58-26fd-473b-8c91-f8250bdee2bd" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_3358c30c-1a85-4849-aef3-867791851a77" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_TradingSymbol_3358c30c-1a85-4849-aef3-867791851a77" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_c359dc02-83b9-4ca0-a3f2-a4ee870224ad" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_SecurityExchangeName_c359dc02-83b9-4ca0-a3f2-a4ee870224ad" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_cb15d185-2288-48fe-b0af-d84b538ee793" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntityCurrentReportingStatus_cb15d185-2288-48fe-b0af-d84b538ee793" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_b6b94ce3-551b-429f-afa4-3ed10c8afd4c" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntityInteractiveDataCurrent_b6b94ce3-551b-429f-afa4-3ed10c8afd4c" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_2266c22d-e439-4b36-8f39-3a04df8d5881" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntityFilerCategory_2266c22d-e439-4b36-8f39-3a04df8d5881" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_0940912a-6040-451e-baa4-b5ff08ea1da1" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntitySmallBusiness_0940912a-6040-451e-baa4-b5ff08ea1da1" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_efa9f764-b98d-4f24-a854-5f6974d7b668" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntityEmergingGrowthCompany_efa9f764-b98d-4f24-a854-5f6974d7b668" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_79c655b6-1118-418b-a220-fa9f0bce841a" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntityShellCompany_79c655b6-1118-418b-a220-fa9f0bce841a" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_b05b5d3e-ee93-4b77-a8a2-d717d28b434d" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_b05b5d3e-ee93-4b77-a8a2-d717d28b434d" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_c2a0f00e-2804-4bdb-b34c-5d5ecf38a173" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_EntityCentralIndexKey_c2a0f00e-2804-4bdb-b34c-5d5ecf38a173" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_63bf1e8d-ac83-4031-b3f8-53c24cd82a06" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_CurrentFiscalYearEndDate_63bf1e8d-ac83-4031-b3f8-53c24cd82a06" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_02a01c92-6121-42b0-bd49-adf1d95af06b" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_DocumentFiscalYearFocus_02a01c92-6121-42b0-bd49-adf1d95af06b" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_3b675ae8-5b8b-44e1-a331-b4feb4000d83" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_DocumentFiscalPeriodFocus_3b675ae8-5b8b-44e1-a331-b4feb4000d83" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_e8454662-f373-41d8-9ccc-11cad99d95c0" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_AmendmentFlag_e8454662-f373-41d8-9ccc-11cad99d95c0" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_b695b444-1d60-47a0-a845-acfd7f7fa9f5" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_e7e97df9-3937-4005-8c55-2c291b57efb5" xlink:to="loc_dei_DocumentInformationTable_b695b444-1d60-47a0-a845-acfd7f7fa9f5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_7eb938fe-0106-41ee-92fa-77894a625ba9" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_b695b444-1d60-47a0-a845-acfd7f7fa9f5" xlink:to="loc_srt_ConsolidatedEntitiesAxis_7eb938fe-0106-41ee-92fa-77894a625ba9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_7eb938fe-0106-41ee-92fa-77894a625ba9_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_7eb938fe-0106-41ee-92fa-77894a625ba9" xlink:to="loc_srt_ConsolidatedEntitiesDomain_7eb938fe-0106-41ee-92fa-77894a625ba9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_c0559519-32c4-435a-a048-34fa42afb948" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_7eb938fe-0106-41ee-92fa-77894a625ba9" xlink:to="loc_srt_ConsolidatedEntitiesDomain_c0559519-32c4-435a-a048-34fa42afb948" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember_ff98ee25-0849-4d61-a4ac-bf92e876b71c" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_c0559519-32c4-435a-a048-34fa42afb948" xlink:to="loc_srt_SubsidiariesMember_ff98ee25-0849-4d61-a4ac-bf92e876b71c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/CONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="simple" xlink:href="bdn-20230630.xsd#CONSOLIDATEDSTATEMENTSOFOPERATIONS"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/CONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="extended" id="i296de61445284f1191f34b601e0aa6dc_CONSOLIDATEDSTATEMENTSOFOPERATIONS">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_aeb32956-5fd5-40a2-9e6d-311be1dc30bb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_us-gaap_RevenuesAbstract_aeb32956-5fd5-40a2-9e6d-311be1dc30bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_57e9998b-c43e-4015-93c3-5348a5392de5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_aeb32956-5fd5-40a2-9e6d-311be1dc30bb" xlink:to="loc_us-gaap_Revenues_57e9998b-c43e-4015-93c3-5348a5392de5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_d8847874-4466-4d9e-aef1-415bf1dfc166" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_d8847874-4466-4d9e-aef1-415bf1dfc166" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfOtherPropertyOperatingExpense_5a41a09c-1381-4600-ac56-9378eff60320" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfOtherPropertyOperatingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_d8847874-4466-4d9e-aef1-415bf1dfc166" xlink:to="loc_us-gaap_CostOfOtherPropertyOperatingExpense_5a41a09c-1381-4600-ac56-9378eff60320" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateTaxExpense_b7b08f8f-dbb3-43b5-8971-e76c6f29a043" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateTaxExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_d8847874-4466-4d9e-aef1-415bf1dfc166" xlink:to="loc_us-gaap_RealEstateTaxExpense_b7b08f8f-dbb3-43b5-8971-e76c6f29a043" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_ThirdPartyManagementExpenses_4fe028c5-4290-4c74-8055-daa464592ab0" xlink:href="bdn-20230630.xsd#bdn_ThirdPartyManagementExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_d8847874-4466-4d9e-aef1-415bf1dfc166" xlink:to="loc_bdn_ThirdPartyManagementExpenses_4fe028c5-4290-4c74-8055-daa464592ab0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_34cee700-6c76-43f7-a0c6-4c97364697cb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_d8847874-4466-4d9e-aef1-415bf1dfc166" xlink:to="loc_us-gaap_DepreciationAndAmortization_34cee700-6c76-43f7-a0c6-4c97364697cb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_aed97159-b19b-4135-bb75-6f8b124de3e8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_d8847874-4466-4d9e-aef1-415bf1dfc166" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_aed97159-b19b-4135-bb75-6f8b124de3e8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetImpairmentCharges_7c0ac205-16ad-4a34-8569-7318ab32ba2f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_d8847874-4466-4d9e-aef1-415bf1dfc166" xlink:to="loc_us-gaap_AssetImpairmentCharges_7c0ac205-16ad-4a34-8569-7318ab32ba2f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_a81bc9c6-5442-437c-9e1b-c52efbd3c70c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_d8847874-4466-4d9e-aef1-415bf1dfc166" xlink:to="loc_us-gaap_CostsAndExpenses_a81bc9c6-5442-437c-9e1b-c52efbd3c70c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_GainLossOnSaleOfPropertiesAbstract_5c42dac3-a2f9-4fd8-a101-ce36722de5e5" xlink:href="bdn-20230630.xsd#bdn_GainLossOnSaleOfPropertiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_bdn_GainLossOnSaleOfPropertiesAbstract_5c42dac3-a2f9-4fd8-a101-ce36722de5e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_aa93fa9b-7cba-4251-8d9a-4cb259d7698b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_GainLossOnSaleOfPropertiesAbstract_5c42dac3-a2f9-4fd8-a101-ce36722de5e5" xlink:to="loc_us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_aa93fa9b-7cba-4251-8d9a-4cb259d7698b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_NetGainLossOnSaleOfUndepreciatedRealEstate_b9e07e5b-c8fb-4630-9145-fc840981773d" xlink:href="bdn-20230630.xsd#bdn_NetGainLossOnSaleOfUndepreciatedRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_GainLossOnSaleOfPropertiesAbstract_5c42dac3-a2f9-4fd8-a101-ce36722de5e5" xlink:to="loc_bdn_NetGainLossOnSaleOfUndepreciatedRealEstate_b9e07e5b-c8fb-4630-9145-fc840981773d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfProperties_9b324d89-92e3-4ddc-b147-54b352d7144a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnSaleOfProperties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_GainLossOnSaleOfPropertiesAbstract_5c42dac3-a2f9-4fd8-a101-ce36722de5e5" xlink:to="loc_us-gaap_GainLossOnSaleOfProperties_9b324d89-92e3-4ddc-b147-54b352d7144a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_52f24b22-3461-40d7-b5a7-b7d4ad467988" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_us-gaap_OperatingIncomeLoss_52f24b22-3461-40d7-b5a7-b7d4ad467988" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpenseAbstract_81e19a97-f229-4053-a8a1-1d0e8e6e863b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonoperatingIncomeExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_us-gaap_NonoperatingIncomeExpenseAbstract_81e19a97-f229-4053-a8a1-1d0e8e6e863b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeNet_5a6d10d7-634b-490a-8cac-75ad290cc68f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_81e19a97-f229-4053-a8a1-1d0e8e6e863b" xlink:to="loc_us-gaap_InvestmentIncomeNet_5a6d10d7-634b-490a-8cac-75ad290cc68f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseOther_b3138b49-59b4-48c7-bb17-9162bf687688" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpenseOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_81e19a97-f229-4053-a8a1-1d0e8e6e863b" xlink:to="loc_us-gaap_InterestExpenseOther_b3138b49-59b4-48c7-bb17-9162bf687688" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_aba7e025-aedb-4aab-a583-85b78b2b7989" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_81e19a97-f229-4053-a8a1-1d0e8e6e863b" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_aba7e025-aedb-4aab-a583-85b78b2b7989" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_1eba4dd8-c552-4233-816a-6abe27628bbe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_81e19a97-f229-4053-a8a1-1d0e8e6e863b" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_1eba4dd8-c552-4233-816a-6abe27628bbe" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_NetGainLossOnRealEstateVentureTransactionsIncludingRealEstateVentureFormation_5de72c3d-6a77-40cf-9124-fa902fee337b" xlink:href="bdn-20230630.xsd#bdn_NetGainLossOnRealEstateVentureTransactionsIncludingRealEstateVentureFormation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_81e19a97-f229-4053-a8a1-1d0e8e6e863b" xlink:to="loc_bdn_NetGainLossOnRealEstateVentureTransactionsIncludingRealEstateVentureFormation_5de72c3d-6a77-40cf-9124-fa902fee337b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_18abc68f-5623-42e3-a259-6ae2ed4bfed1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_18abc68f-5623-42e3-a259-6ae2ed4bfed1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_1c5a6aba-50d6-4e0d-8724-d609db05c617" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_1c5a6aba-50d6-4e0d-8724-d609db05c617" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_806acc95-8cbf-4fc3-8db3-7ecfeec1749e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_us-gaap_ProfitLoss_806acc95-8cbf-4fc3-8db3-7ecfeec1749e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_d8c50f8e-666d-4813-b484-8b9f8187382d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_d8c50f8e-666d-4813-b484-8b9f8187382d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_ae83306b-6144-4486-b829-6ac03187710b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_us-gaap_NetIncomeLoss_ae83306b-6144-4486-b829-6ac03187710b" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic_33bc7576-69d6-4cde-bd5d-7059d52bb31d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic_33bc7576-69d6-4cde-bd5d-7059d52bb31d" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_edb9b801-49cb-4aed-a403-9110e97f6563" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_edb9b801-49cb-4aed-a403-9110e97f6563" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_dc2821bd-b466-4761-9697-0bf1e94a0468" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_us-gaap_EarningsPerShareBasic_dc2821bd-b466-4761-9697-0bf1e94a0468" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_1f115db3-9987-4400-b8cf-0aff8600f83d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_us-gaap_EarningsPerShareDiluted_1f115db3-9987-4400-b8cf-0aff8600f83d" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_16c10020-c2d5-4458-8bc6-0d3402678e4d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_16c10020-c2d5-4458-8bc6-0d3402678e4d" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_12f13226-872b-4305-bac4-e56067dceba8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_12f13226-872b-4305-bac4-e56067dceba8" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_c1f36549-49c8-4039-8017-0d52215a506f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_3cdebaef-6ed0-4d76-8637-fa7b08a77f01" xlink:to="loc_us-gaap_StatementTable_c1f36549-49c8-4039-8017-0d52215a506f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_9a155a49-1c76-439f-9ac9-c2cf2227cec6" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_c1f36549-49c8-4039-8017-0d52215a506f" xlink:to="loc_srt_ProductOrServiceAxis_9a155a49-1c76-439f-9ac9-c2cf2227cec6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_9a155a49-1c76-439f-9ac9-c2cf2227cec6_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_9a155a49-1c76-439f-9ac9-c2cf2227cec6" xlink:to="loc_srt_ProductsAndServicesDomain_9a155a49-1c76-439f-9ac9-c2cf2227cec6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_4683dd5b-75e3-42e6-b749-45569ac00dd8" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_9a155a49-1c76-439f-9ac9-c2cf2227cec6" xlink:to="loc_srt_ProductsAndServicesDomain_4683dd5b-75e3-42e6-b749-45569ac00dd8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_RentsMember_9a9da41a-4406-489e-af20-f6582cd9f2e7" xlink:href="bdn-20230630.xsd#bdn_RentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_4683dd5b-75e3-42e6-b749-45569ac00dd8" xlink:to="loc_bdn_RentsMember_9a9da41a-4406-489e-af20-f6582cd9f2e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_ThirdPartyManagementRevenueMember_f0701942-be1f-4e35-98e8-3a27bd96bb0a" xlink:href="bdn-20230630.xsd#bdn_ThirdPartyManagementRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_4683dd5b-75e3-42e6-b749-45569ac00dd8" xlink:to="loc_bdn_ThirdPartyManagementRevenueMember_f0701942-be1f-4e35-98e8-3a27bd96bb0a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateOtherMember_3049c16e-8ad9-4b43-a085-33dd9dd817f0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_4683dd5b-75e3-42e6-b749-45569ac00dd8" xlink:to="loc_us-gaap_RealEstateOtherMember_3049c16e-8ad9-4b43-a085-33dd9dd817f0" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/CONSOLIDATEDSTATEMENTSOFBENEFICIARIESEQUITY" xlink:type="simple" xlink:href="bdn-20230630.xsd#CONSOLIDATEDSTATEMENTSOFBENEFICIARIESEQUITY"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/CONSOLIDATEDSTATEMENTSOFBENEFICIARIESEQUITY" xlink:type="extended" id="i0b637f7b26d0401894b90645d441749a_CONSOLIDATEDSTATEMENTSOFBENEFICIARIESEQUITY">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_deac4071-f1f6-4fa0-a4bc-3f0022696bc2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2851517e-3032-44b2-b012-5ffdae9b75d8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_deac4071-f1f6-4fa0-a4bc-3f0022696bc2" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2851517e-3032-44b2-b012-5ffdae9b75d8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_629b91b0-1a20-48f3-9031-4315e9779364" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2851517e-3032-44b2-b012-5ffdae9b75d8" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_629b91b0-1a20-48f3-9031-4315e9779364" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_09bf643e-50f1-435e-9e0f-6df9eb1aeab2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2851517e-3032-44b2-b012-5ffdae9b75d8" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_09bf643e-50f1-435e-9e0f-6df9eb1aeab2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_9d45f3b6-7608-4ba9-9a8d-8625c220bb5c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2851517e-3032-44b2-b012-5ffdae9b75d8" xlink:to="loc_us-gaap_ProfitLoss_9d45f3b6-7608-4ba9-9a8d-8625c220bb5c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_db28357d-cfc3-481d-b34c-ae1619c3f7bf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2851517e-3032-44b2-b012-5ffdae9b75d8" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_db28357d-cfc3-481d-b34c-ae1619c3f7bf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_StockIssuedDuringPeriodValueRedemptionOfLimitedPartnersUnits_f3ed86da-fbe0-4a13-a06e-3fa66d0aff41" xlink:href="bdn-20230630.xsd#bdn_StockIssuedDuringPeriodValueRedemptionOfLimitedPartnersUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2851517e-3032-44b2-b012-5ffdae9b75d8" xlink:to="loc_bdn_StockIssuedDuringPeriodValueRedemptionOfLimitedPartnersUnits_f3ed86da-fbe0-4a13-a06e-3fa66d0aff41" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_2754d970-437f-4a00-9948-4a4b059c1343" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2851517e-3032-44b2-b012-5ffdae9b75d8" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_2754d970-437f-4a00-9948-4a4b059c1343" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_2741aca5-8e31-4052-932c-fa53720d977f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2851517e-3032-44b2-b012-5ffdae9b75d8" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_2741aca5-8e31-4052-932c-fa53720d977f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_ShareIssuanceFromToDeferredCompensationPlanShares_fb2e693a-4b27-4555-a0cc-5c9e5d07fc40" xlink:href="bdn-20230630.xsd#bdn_ShareIssuanceFromToDeferredCompensationPlanShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2851517e-3032-44b2-b012-5ffdae9b75d8" xlink:to="loc_bdn_ShareIssuanceFromToDeferredCompensationPlanShares_fb2e693a-4b27-4555-a0cc-5c9e5d07fc40" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_ShareIssuanceFromToDeferredCompensationPlan_3fe27661-61a2-4688-ba3b-4e90091f6302" xlink:href="bdn-20230630.xsd#bdn_ShareIssuanceFromToDeferredCompensationPlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2851517e-3032-44b2-b012-5ffdae9b75d8" xlink:to="loc_bdn_ShareIssuanceFromToDeferredCompensationPlan_3fe27661-61a2-4688-ba3b-4e90091f6302" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_NoncontrollingInterestIncreaseDecreaseFromReallocation_53b9feae-54e2-4113-a78f-5a0190f4abb1" xlink:href="bdn-20230630.xsd#bdn_NoncontrollingInterestIncreaseDecreaseFromReallocation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2851517e-3032-44b2-b012-5ffdae9b75d8" xlink:to="loc_bdn_NoncontrollingInterestIncreaseDecreaseFromReallocation_53b9feae-54e2-4113-a78f-5a0190f4abb1" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_6f80f7c5-857a-4d6f-a460-9635c78512f7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsCommonStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_2851517e-3032-44b2-b012-5ffdae9b75d8" xlink:to="loc_us-gaap_DividendsCommonStockCash_6f80f7c5-857a-4d6f-a460-9635c78512f7" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_e1d2adb4-1f56-4357-bffe-8c29af77e9f1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_2a9584c8-5f95-45c5-af11-661625c38648" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_081529cb-b28a-4f6e-9d1a-3244a1f48047" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_deac4071-f1f6-4fa0-a4bc-3f0022696bc2" xlink:to="loc_us-gaap_StatementTable_081529cb-b28a-4f6e-9d1a-3244a1f48047" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_71a1f3fe-a60d-4614-8abf-2b39772876eb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_081529cb-b28a-4f6e-9d1a-3244a1f48047" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_71a1f3fe-a60d-4614-8abf-2b39772876eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_71a1f3fe-a60d-4614-8abf-2b39772876eb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_71a1f3fe-a60d-4614-8abf-2b39772876eb" xlink:to="loc_us-gaap_EquityComponentDomain_71a1f3fe-a60d-4614-8abf-2b39772876eb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_9c19f643-43ee-44ef-a024-70ccd6a89934" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_71a1f3fe-a60d-4614-8abf-2b39772876eb" xlink:to="loc_us-gaap_EquityComponentDomain_9c19f643-43ee-44ef-a024-70ccd6a89934" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_dfeb91a3-ae7f-4cec-b606-69d6528dbfe0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_9c19f643-43ee-44ef-a024-70ccd6a89934" xlink:to="loc_us-gaap_CommonStockMember_dfeb91a3-ae7f-4cec-b606-69d6528dbfe0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationShareBasedPaymentsMember_3040dfa4-0ff0-462f-8f44-a2315a00ba64" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredCompensationShareBasedPaymentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_9c19f643-43ee-44ef-a024-70ccd6a89934" xlink:to="loc_us-gaap_DeferredCompensationShareBasedPaymentsMember_3040dfa4-0ff0-462f-8f44-a2315a00ba64" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_14c8a64f-05a8-467d-aeae-4bae52463668" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_9c19f643-43ee-44ef-a024-70ccd6a89934" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_14c8a64f-05a8-467d-aeae-4bae52463668" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_CommonStockHeldInTrustMember_a44eaa6e-c945-4ddc-858f-4253822934ef" xlink:href="bdn-20230630.xsd#bdn_CommonStockHeldInTrustMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_9c19f643-43ee-44ef-a024-70ccd6a89934" xlink:to="loc_bdn_CommonStockHeldInTrustMember_a44eaa6e-c945-4ddc-858f-4253822934ef" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_957e3805-44b7-4606-be32-b2aae81f7408" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_9c19f643-43ee-44ef-a024-70ccd6a89934" xlink:to="loc_us-gaap_RetainedEarningsMember_957e3805-44b7-4606-be32-b2aae81f7408" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_4902306e-59e4-4b61-b4ee-bd5a47a9fd28" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_9c19f643-43ee-44ef-a024-70ccd6a89934" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_4902306e-59e4-4b61-b4ee-bd5a47a9fd28" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDistributionsInExcessOfNetIncomeMember_b10f6e90-5f3b-40b7-b6ec-4686f33a0fe3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedDistributionsInExcessOfNetIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_9c19f643-43ee-44ef-a024-70ccd6a89934" xlink:to="loc_us-gaap_AccumulatedDistributionsInExcessOfNetIncomeMember_b10f6e90-5f3b-40b7-b6ec-4686f33a0fe3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_ae60ea55-4c1d-43c1-86c5-6a39afc5ad62" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_9c19f643-43ee-44ef-a024-70ccd6a89934" xlink:to="loc_us-gaap_NoncontrollingInterestMember_ae60ea55-4c1d-43c1-86c5-6a39afc5ad62" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/CONSOLIDATEDBALANCESHEETSBRANDYWINEOPERATINGPARTNERSHIPLP" xlink:type="simple" xlink:href="bdn-20230630.xsd#CONSOLIDATEDBALANCESHEETSBRANDYWINEOPERATINGPARTNERSHIPLP"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/CONSOLIDATEDBALANCESHEETSBRANDYWINEOPERATINGPARTNERSHIPLP" xlink:type="extended" id="iec9a2bf791f2457a9df17fb5358ea626_CONSOLIDATEDBALANCESHEETSBRANDYWINEOPERATINGPARTNERSHIPLP">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_0829cefc-ecc9-4459-ab52-ac1666a65956" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_2cfad861-4be6-4299-b919-70c084515f9d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0829cefc-ecc9-4459-ab52-ac1666a65956" xlink:to="loc_us-gaap_AssetsAbstract_2cfad861-4be6-4299-b919-70c084515f9d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentsAbstract_c0fb766e-28bf-4a5b-8fed-79a03e03c22d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateInvestmentsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2cfad861-4be6-4299-b919-70c084515f9d" xlink:to="loc_us-gaap_RealEstateInvestmentsAbstract_c0fb766e-28bf-4a5b-8fed-79a03e03c22d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyAtCost_072e1b66-fda5-4aa7-81c6-45ae9f3cf7c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateInvestmentPropertyAtCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstateInvestmentsAbstract_c0fb766e-28bf-4a5b-8fed-79a03e03c22d" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyAtCost_072e1b66-fda5-4aa7-81c6-45ae9f3cf7c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation_0fa01085-01dd-4118-a136-904dd64e11ae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstateInvestmentsAbstract_c0fb766e-28bf-4a5b-8fed-79a03e03c22d" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation_0fa01085-01dd-4118-a136-904dd64e11ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_1004520e-664e-48e8-ab06-93548db2c11e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstateInvestmentsAbstract_c0fb766e-28bf-4a5b-8fed-79a03e03c22d" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_1004520e-664e-48e8-ab06-93548db2c11e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_OperatingRealEstateInvestmentPropertyNet_2798c112-bf94-4b51-a832-26dca0c04c5d" xlink:href="bdn-20230630.xsd#bdn_OperatingRealEstateInvestmentPropertyNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstateInvestmentsAbstract_c0fb766e-28bf-4a5b-8fed-79a03e03c22d" xlink:to="loc_bdn_OperatingRealEstateInvestmentPropertyNet_2798c112-bf94-4b51-a832-26dca0c04c5d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopmentInProcess_ef4ffe58-ded5-4e5d-8d93-592e80b56e63" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DevelopmentInProcess"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstateInvestmentsAbstract_c0fb766e-28bf-4a5b-8fed-79a03e03c22d" xlink:to="loc_us-gaap_DevelopmentInProcess_ef4ffe58-ded5-4e5d-8d93-592e80b56e63" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandAvailableForDevelopment_2e473315-829b-45ef-ac78-0d82d1adea44" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LandAvailableForDevelopment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstateInvestmentsAbstract_c0fb766e-28bf-4a5b-8fed-79a03e03c22d" xlink:to="loc_us-gaap_LandAvailableForDevelopment_2e473315-829b-45ef-ac78-0d82d1adea44" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseCurrentAndNoncurrent_80933b53-ea69-4ce2-91dd-5bc05150ab39" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PrepaidExpenseCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstateInvestmentsAbstract_c0fb766e-28bf-4a5b-8fed-79a03e03c22d" xlink:to="loc_us-gaap_PrepaidExpenseCurrentAndNoncurrent_80933b53-ea69-4ce2-91dd-5bc05150ab39" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyNet_0a70aef1-f7cc-4946-bda9-89d22f4c3cac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateInvestmentPropertyNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstateInvestmentsAbstract_c0fb766e-28bf-4a5b-8fed-79a03e03c22d" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyNet_0a70aef1-f7cc-4946-bda9-89d22f4c3cac" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation_9422deb7-d543-483f-9970-cbb56a8e6f41" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2cfad861-4be6-4299-b919-70c084515f9d" xlink:to="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation_9422deb7-d543-483f-9970-cbb56a8e6f41" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_8f082529-47d5-4365-bb4a-d65f71901ffa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2cfad861-4be6-4299-b919-70c084515f9d" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_8f082529-47d5-4365-bb4a-d65f71901ffa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash_9d891ed7-8e3b-497a-9763-2f7f55df71bf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2cfad861-4be6-4299-b919-70c084515f9d" xlink:to="loc_us-gaap_RestrictedCash_9d891ed7-8e3b-497a-9763-2f7f55df71bf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNet_ec14889e-96b4-4212-9b9c-c79d8153685d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2cfad861-4be6-4299-b919-70c084515f9d" xlink:to="loc_us-gaap_AccountsReceivableNet_ec14889e-96b4-4212-9b9c-c79d8153685d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredRentReceivablesNet_7c57c835-eea2-4a5f-a316-e0303c112916" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredRentReceivablesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2cfad861-4be6-4299-b919-70c084515f9d" xlink:to="loc_us-gaap_DeferredRentReceivablesNet_7c57c835-eea2-4a5f-a316-e0303c112916" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_EquityMethodInvestmentsInAssetPosition_d0cef0c8-c639-4c00-b393-deac4189e8c2" xlink:href="bdn-20230630.xsd#bdn_EquityMethodInvestmentsInAssetPosition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2cfad861-4be6-4299-b919-70c084515f9d" xlink:to="loc_bdn_EquityMethodInvestmentsInAssetPosition_d0cef0c8-c639-4c00-b393-deac4189e8c2" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCostsCurrentAndNoncurrent_353d3282-2a42-44b7-abdf-afe5ae45bd7c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredCostsCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2cfad861-4be6-4299-b919-70c084515f9d" xlink:to="loc_us-gaap_DeferredCostsCurrentAndNoncurrent_353d3282-2a42-44b7-abdf-afe5ae45bd7c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_FiniteLivedIntangibleAssetsNetContinuingOperations_c853cb07-2d06-433a-bfa4-2f29d314bf3d" xlink:href="bdn-20230630.xsd#bdn_FiniteLivedIntangibleAssetsNetContinuingOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2cfad861-4be6-4299-b919-70c084515f9d" xlink:to="loc_bdn_FiniteLivedIntangibleAssetsNetContinuingOperations_c853cb07-2d06-433a-bfa4-2f29d314bf3d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_65b5a050-738c-47f6-9886-9b2b2e64628f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2cfad861-4be6-4299-b919-70c084515f9d" xlink:to="loc_us-gaap_OtherAssets_65b5a050-738c-47f6-9886-9b2b2e64628f" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_de22c6cb-65dd-4ec2-a0f1-0b361ffd5c94" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2cfad861-4be6-4299-b919-70c084515f9d" xlink:to="loc_us-gaap_Assets_de22c6cb-65dd-4ec2-a0f1-0b361ffd5c94" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0829cefc-ecc9-4459-ab52-ac1666a65956" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebt_aaed0d3e-2e33-4722-9e46-7d4cebfe8d05" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:to="loc_us-gaap_SecuredDebt_aaed0d3e-2e33-4722-9e46-7d4cebfe8d05" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_d7328ee2-3982-4e6f-af6d-ee0b8d20a2db" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:to="loc_us-gaap_LineOfCredit_d7328ee2-3982-4e6f-af6d-ee0b8d20a2db" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebt_9ce9f515-4eac-4aa2-bc17-04002d0293c5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnsecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:to="loc_us-gaap_UnsecuredDebt_9ce9f515-4eac-4aa2-bc17-04002d0293c5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotes_7325e659-5632-42e7-adc9-6f95d87858a3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeniorNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:to="loc_us-gaap_SeniorNotes_7325e659-5632-42e7-adc9-6f95d87858a3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_eeb4c827-8970-49f8-8613-566f7a31deca" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:to="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_eeb4c827-8970-49f8-8613-566f7a31deca" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPayableCurrentAndNoncurrent_06da03d9-546e-4e77-aba3-f38d93dd41ee" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:to="loc_us-gaap_DividendsPayableCurrentAndNoncurrent_06da03d9-546e-4e77-aba3-f38d93dd41ee" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_556b6d03-342c-4ccc-9435-2b9b85f15e05" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:to="loc_us-gaap_ContractWithCustomerLiability_556b6d03-342c-4ccc-9435-2b9b85f15e05" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_BelowMarketLeaseNetOperatingActivities_44368cdf-1103-435f-a732-23b24538bf35" xlink:href="bdn-20230630.xsd#bdn_BelowMarketLeaseNetOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:to="loc_bdn_BelowMarketLeaseNetOperatingActivities_44368cdf-1103-435f-a732-23b24538bf35" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation_0172cd18-1fdf-4ec0-8668-cb1146c5870c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:to="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation_0172cd18-1fdf-4ec0-8668-cb1146c5870c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_2acc62aa-4e52-4dd6-a11c-6fda148ed4d8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:to="loc_us-gaap_OperatingLeaseLiability_2acc62aa-4e52-4dd6-a11c-6fda148ed4d8" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities_94d66b87-315a-404e-9ed4-4a3b227967c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:to="loc_us-gaap_OtherLiabilities_94d66b87-315a-404e-9ed4-4a3b227967c8" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_24c70564-0d28-4b2a-b208-b9347e0b02e1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:to="loc_us-gaap_Liabilities_24c70564-0d28-4b2a-b208-b9347e0b02e1" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_6e173ef1-3cac-489f-8c10-b7f8e6ba6b52" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:to="loc_us-gaap_CommitmentsAndContingencies_6e173ef1-3cac-489f-8c10-b7f8e6ba6b52" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityCarryingAmountIncludingPortionAttributableToNoncontrollingInterests_860f7a18-03a1-49bb-8b40-17084802712e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TemporaryEquityCarryingAmountIncludingPortionAttributableToNoncontrollingInterests"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:to="loc_us-gaap_TemporaryEquityCarryingAmountIncludingPortionAttributableToNoncontrollingInterests_860f7a18-03a1-49bb-8b40-17084802712e" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityAbstract_bc2c4a91-16ae-4dab-9680-f0ced0106149" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:to="loc_us-gaap_EquityAbstract_bc2c4a91-16ae-4dab-9680-f0ced0106149" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralPartnersCapitalAccount_0d37710f-8a90-40a5-90da-b87d168f9576" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralPartnersCapitalAccount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_bc2c4a91-16ae-4dab-9680-f0ced0106149" xlink:to="loc_us-gaap_GeneralPartnersCapitalAccount_0d37710f-8a90-40a5-90da-b87d168f9576" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_f919c276-f333-4b16-bb30-14a2d8702e83" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_bc2c4a91-16ae-4dab-9680-f0ced0106149" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_f919c276-f333-4b16-bb30-14a2d8702e83" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapital_b2e7f991-130d-4e1a-8fe5-821ac497aa7d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_bc2c4a91-16ae-4dab-9680-f0ced0106149" xlink:to="loc_us-gaap_PartnersCapital_b2e7f991-130d-4e1a-8fe5-821ac497aa7d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAttributableToNoncontrollingInterest_10ed6d14-c3ca-4997-825b-7cdc1b786d1b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapitalAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_bc2c4a91-16ae-4dab-9680-f0ced0106149" xlink:to="loc_us-gaap_PartnersCapitalAttributableToNoncontrollingInterest_10ed6d14-c3ca-4997-825b-7cdc1b786d1b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_d246cf91-7b75-43c0-aa54-0258bf676ae0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_bc2c4a91-16ae-4dab-9680-f0ced0106149" xlink:to="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_d246cf91-7b75-43c0-aa54-0258bf676ae0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_f8fc1fb2-5b84-4310-b2a6-c1cf0bd4cd02" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7a6a89aa-2e89-4ab1-b46e-d1b8a020be2d" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_f8fc1fb2-5b84-4310-b2a6-c1cf0bd4cd02" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_5018d89b-1a22-4799-8012-6017ac447e69" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_0829cefc-ecc9-4459-ab52-ac1666a65956" xlink:to="loc_us-gaap_StatementTable_5018d89b-1a22-4799-8012-6017ac447e69" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_227ada6e-698a-4a7f-8404-bd90a778d925" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_5018d89b-1a22-4799-8012-6017ac447e69" xlink:to="loc_srt_ConsolidatedEntitiesAxis_227ada6e-698a-4a7f-8404-bd90a778d925" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_227ada6e-698a-4a7f-8404-bd90a778d925_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_227ada6e-698a-4a7f-8404-bd90a778d925" xlink:to="loc_srt_ConsolidatedEntitiesDomain_227ada6e-698a-4a7f-8404-bd90a778d925_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_d58f884a-c473-487b-a112-7d16e0fec2d3" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_227ada6e-698a-4a7f-8404-bd90a778d925" xlink:to="loc_srt_ConsolidatedEntitiesDomain_d58f884a-c473-487b-a112-7d16e0fec2d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember_9e617cfb-b336-429c-9b00-ab7076a26d08" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_d58f884a-c473-487b-a112-7d16e0fec2d3" xlink:to="loc_srt_SubsidiariesMember_9e617cfb-b336-429c-9b00-ab7076a26d08" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/CONSOLIDATEDBALANCESHEETSBRANDYWINEOPERATINGPARTNERSHIPLPParenthetical" xlink:type="simple" xlink:href="bdn-20230630.xsd#CONSOLIDATEDBALANCESHEETSBRANDYWINEOPERATINGPARTNERSHIPLPParenthetical"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/CONSOLIDATEDBALANCESHEETSBRANDYWINEOPERATINGPARTNERSHIPLPParenthetical" xlink:type="extended" id="i763b372332ef4af9a620f0d5e1c6eef4_CONSOLIDATEDBALANCESHEETSBRANDYWINEOPERATINGPARTNERSHIPLPParenthetical">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_d2262633-13e3-403d-b9cd-168be68f525c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_AllowanceForDoubtfulAccruedRentReceivable_eb4089ad-0ec3-4594-8c36-3b30e116a541" xlink:href="bdn-20230630.xsd#bdn_AllowanceForDoubtfulAccruedRentReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_d2262633-13e3-403d-b9cd-168be68f525c" xlink:to="loc_bdn_AllowanceForDoubtfulAccruedRentReceivable_eb4089ad-0ec3-4594-8c36-3b30e116a541" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquitySharesIssued_86ac1d9f-c75e-4084-98c6-e596e7c1653b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TemporaryEquitySharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_d2262633-13e3-403d-b9cd-168be68f525c" xlink:to="loc_us-gaap_TemporaryEquitySharesIssued_86ac1d9f-c75e-4084-98c6-e596e7c1653b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquitySharesOutstanding_af271dcd-f842-42b7-acca-b8b75a749613" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TemporaryEquitySharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_d2262633-13e3-403d-b9cd-168be68f525c" xlink:to="loc_us-gaap_TemporaryEquitySharesOutstanding_af271dcd-f842-42b7-acca-b8b75a749613" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_1517413c-dd70-499d-9c5d-8d711cdbd4b5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_d2262633-13e3-403d-b9cd-168be68f525c" xlink:to="loc_us-gaap_CommonStockSharesIssued_1517413c-dd70-499d-9c5d-8d711cdbd4b5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_904d16a8-0032-4bb3-be39-1e847f9e9e64" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_d2262633-13e3-403d-b9cd-168be68f525c" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_904d16a8-0032-4bb3-be39-1e847f9e9e64" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_310b6671-3fec-4689-89e1-469174f83842" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_d2262633-13e3-403d-b9cd-168be68f525c" xlink:to="loc_us-gaap_StatementTable_310b6671-3fec-4689-89e1-469174f83842" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_9bbcf00f-3be3-4aed-8f77-04ee04343b39" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_310b6671-3fec-4689-89e1-469174f83842" xlink:to="loc_srt_ConsolidatedEntitiesAxis_9bbcf00f-3be3-4aed-8f77-04ee04343b39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_9bbcf00f-3be3-4aed-8f77-04ee04343b39_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_9bbcf00f-3be3-4aed-8f77-04ee04343b39" xlink:to="loc_srt_ConsolidatedEntitiesDomain_9bbcf00f-3be3-4aed-8f77-04ee04343b39_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_292d76c3-12e4-4503-8f99-8a498e2157ef" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_9bbcf00f-3be3-4aed-8f77-04ee04343b39" xlink:to="loc_srt_ConsolidatedEntitiesDomain_292d76c3-12e4-4503-8f99-8a498e2157ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember_12fcb23e-9e4c-4278-92dc-923bc477e721" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_292d76c3-12e4-4503-8f99-8a498e2157ef" xlink:to="loc_srt_SubsidiariesMember_12fcb23e-9e4c-4278-92dc-923bc477e721" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_4d955fb0-0c1f-4f9e-84dc-d85ea04a7350" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_310b6671-3fec-4689-89e1-469174f83842" xlink:to="loc_us-gaap_StatementClassOfStockAxis_4d955fb0-0c1f-4f9e-84dc-d85ea04a7350" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_4d955fb0-0c1f-4f9e-84dc-d85ea04a7350_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_4d955fb0-0c1f-4f9e-84dc-d85ea04a7350" xlink:to="loc_us-gaap_ClassOfStockDomain_4d955fb0-0c1f-4f9e-84dc-d85ea04a7350_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_e5f9c081-a5cb-4751-82bd-1edc03b8f6be" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_4d955fb0-0c1f-4f9e-84dc-d85ea04a7350" xlink:to="loc_us-gaap_ClassOfStockDomain_e5f9c081-a5cb-4751-82bd-1edc03b8f6be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_ClassUnitsMember_d9351801-c1c7-4117-ae7a-8cf88d14dd96" xlink:href="bdn-20230630.xsd#bdn_ClassUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_e5f9c081-a5cb-4751-82bd-1edc03b8f6be" xlink:to="loc_bdn_ClassUnitsMember_d9351801-c1c7-4117-ae7a-8cf88d14dd96" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/CONSOLIDATEDSTATEMENTSOFOPERATIONSBRANDYWINEOPERATINGPARTNERSHIPLP" xlink:type="simple" xlink:href="bdn-20230630.xsd#CONSOLIDATEDSTATEMENTSOFOPERATIONSBRANDYWINEOPERATINGPARTNERSHIPLP"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/CONSOLIDATEDSTATEMENTSOFOPERATIONSBRANDYWINEOPERATINGPARTNERSHIPLP" xlink:type="extended" id="i825d463ecf9f403bb4a02cbecf94a06d_CONSOLIDATEDSTATEMENTSOFOPERATIONSBRANDYWINEOPERATINGPARTNERSHIPLP">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_e38dfb10-8106-456b-9eee-b3883d0be018" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_us-gaap_RevenuesAbstract_e38dfb10-8106-456b-9eee-b3883d0be018" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_46cce324-b4c4-4723-b40e-f7df94de25c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_e38dfb10-8106-456b-9eee-b3883d0be018" xlink:to="loc_us-gaap_Revenues_46cce324-b4c4-4723-b40e-f7df94de25c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_1495b3ff-dd4b-4338-8f8b-9816749220a4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_1495b3ff-dd4b-4338-8f8b-9816749220a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfOtherPropertyOperatingExpense_be395c1b-8650-4016-b39c-51c46ce0f608" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfOtherPropertyOperatingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_1495b3ff-dd4b-4338-8f8b-9816749220a4" xlink:to="loc_us-gaap_CostOfOtherPropertyOperatingExpense_be395c1b-8650-4016-b39c-51c46ce0f608" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateTaxExpense_924d3df5-9f37-43ec-8b5c-ae039c8102f1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateTaxExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_1495b3ff-dd4b-4338-8f8b-9816749220a4" xlink:to="loc_us-gaap_RealEstateTaxExpense_924d3df5-9f37-43ec-8b5c-ae039c8102f1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_ThirdPartyManagementExpenses_8207670e-6640-476d-aedc-47105b894469" xlink:href="bdn-20230630.xsd#bdn_ThirdPartyManagementExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_1495b3ff-dd4b-4338-8f8b-9816749220a4" xlink:to="loc_bdn_ThirdPartyManagementExpenses_8207670e-6640-476d-aedc-47105b894469" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_7b22bbb4-bf4e-4e6b-90b1-ff879c8b855b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_1495b3ff-dd4b-4338-8f8b-9816749220a4" xlink:to="loc_us-gaap_DepreciationAndAmortization_7b22bbb4-bf4e-4e6b-90b1-ff879c8b855b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_578f3096-70a0-49f3-9724-0736123b4580" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_1495b3ff-dd4b-4338-8f8b-9816749220a4" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_578f3096-70a0-49f3-9724-0736123b4580" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetImpairmentCharges_be94d2ad-3009-4f40-bdc7-8681ed74b9e1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_1495b3ff-dd4b-4338-8f8b-9816749220a4" xlink:to="loc_us-gaap_AssetImpairmentCharges_be94d2ad-3009-4f40-bdc7-8681ed74b9e1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_86f84160-6ae4-4f86-a522-ad61ef77c9ea" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_1495b3ff-dd4b-4338-8f8b-9816749220a4" xlink:to="loc_us-gaap_CostsAndExpenses_86f84160-6ae4-4f86-a522-ad61ef77c9ea" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_GainLossOnSaleOfPropertiesAbstract_18d839f8-ba20-4c2e-9309-a666e1e5c0a3" xlink:href="bdn-20230630.xsd#bdn_GainLossOnSaleOfPropertiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_bdn_GainLossOnSaleOfPropertiesAbstract_18d839f8-ba20-4c2e-9309-a666e1e5c0a3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_e67d8ab0-20ca-4536-8f93-a9e4806cd195" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_GainLossOnSaleOfPropertiesAbstract_18d839f8-ba20-4c2e-9309-a666e1e5c0a3" xlink:to="loc_us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_e67d8ab0-20ca-4536-8f93-a9e4806cd195" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_NetGainLossOnSaleOfUndepreciatedRealEstate_88870c01-dbd6-425f-8f7f-cb994aaa7b73" xlink:href="bdn-20230630.xsd#bdn_NetGainLossOnSaleOfUndepreciatedRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_GainLossOnSaleOfPropertiesAbstract_18d839f8-ba20-4c2e-9309-a666e1e5c0a3" xlink:to="loc_bdn_NetGainLossOnSaleOfUndepreciatedRealEstate_88870c01-dbd6-425f-8f7f-cb994aaa7b73" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfProperties_81010107-9f76-4930-add3-96360eb8b732" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnSaleOfProperties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_GainLossOnSaleOfPropertiesAbstract_18d839f8-ba20-4c2e-9309-a666e1e5c0a3" xlink:to="loc_us-gaap_GainLossOnSaleOfProperties_81010107-9f76-4930-add3-96360eb8b732" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_543f239d-6fbd-4a1e-a0d7-f8a55fc86d4e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_us-gaap_OperatingIncomeLoss_543f239d-6fbd-4a1e-a0d7-f8a55fc86d4e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpenseAbstract_d86a3232-4cc2-42a7-a29d-a7ca2b4dca71" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonoperatingIncomeExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_us-gaap_NonoperatingIncomeExpenseAbstract_d86a3232-4cc2-42a7-a29d-a7ca2b4dca71" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeNet_13e282db-08d3-40c4-856c-b10e277f28e3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_d86a3232-4cc2-42a7-a29d-a7ca2b4dca71" xlink:to="loc_us-gaap_InvestmentIncomeNet_13e282db-08d3-40c4-856c-b10e277f28e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseOther_bade96e2-577d-4696-b322-4e9dedf0b8a4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpenseOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_d86a3232-4cc2-42a7-a29d-a7ca2b4dca71" xlink:to="loc_us-gaap_InterestExpenseOther_bade96e2-577d-4696-b322-4e9dedf0b8a4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_636e2a68-6c8e-48b5-b65f-6650a9df41dd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_d86a3232-4cc2-42a7-a29d-a7ca2b4dca71" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_636e2a68-6c8e-48b5-b65f-6650a9df41dd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_eab3b5b4-508d-4dc0-8e70-c4c4f1b26e33" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_d86a3232-4cc2-42a7-a29d-a7ca2b4dca71" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_eab3b5b4-508d-4dc0-8e70-c4c4f1b26e33" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_NetGainLossOnRealEstateVentureTransactionsIncludingRealEstateVentureFormation_d7d517aa-bfad-411a-bf76-9349822cb2b6" xlink:href="bdn-20230630.xsd#bdn_NetGainLossOnRealEstateVentureTransactionsIncludingRealEstateVentureFormation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_d86a3232-4cc2-42a7-a29d-a7ca2b4dca71" xlink:to="loc_bdn_NetGainLossOnRealEstateVentureTransactionsIncludingRealEstateVentureFormation_d7d517aa-bfad-411a-bf76-9349822cb2b6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_f6a32f82-8528-4322-9797-f2ae8cdc4f5c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_f6a32f82-8528-4322-9797-f2ae8cdc4f5c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_6f8f33e7-7f2a-48db-8dbb-db8607f51d84" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_6f8f33e7-7f2a-48db-8dbb-db8607f51d84" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_e6ba52d5-2d65-4a6f-bf3e-80e59fb26135" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_us-gaap_ProfitLoss_e6ba52d5-2d65-4a6f-bf3e-80e59fb26135" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity_47aa11d0-8d08-4307-bcb7-ed29e11755fb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity_47aa11d0-8d08-4307-bcb7-ed29e11755fb" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAllocatedToLimitedPartners_06b20da0-2596-4ea9-b2ab-743674c0de44" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLossAllocatedToLimitedPartners"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_us-gaap_NetIncomeLossAllocatedToLimitedPartners_06b20da0-2596-4ea9-b2ab-743674c0de44" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic_f7e72066-dd4d-4ba2-a6ae-987f52a804ac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic_f7e72066-dd4d-4ba2-a6ae-987f52a804ac" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_927a99ec-f353-444e-9ee0-a0597f989de0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_927a99ec-f353-444e-9ee0-a0597f989de0" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_5af5948c-ce04-4311-8a1a-b87dcf349ebc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_us-gaap_EarningsPerShareBasic_5af5948c-ce04-4311-8a1a-b87dcf349ebc" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_29fee3ef-c276-4b27-92da-7a1949edd120" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_us-gaap_EarningsPerShareDiluted_29fee3ef-c276-4b27-92da-7a1949edd120" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_67f6ab8a-96dd-4ea9-8e99-6e4f2f5fd6b5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_67f6ab8a-96dd-4ea9-8e99-6e4f2f5fd6b5" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_9b1e5d6b-df49-43ab-8f84-cf461e4aca9d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_9b1e5d6b-df49-43ab-8f84-cf461e4aca9d" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_8ca30047-b8e9-41f6-8448-f3042e87bfd1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_0d6e709f-b4a1-4d2f-a32d-89076476349d" xlink:to="loc_us-gaap_StatementTable_8ca30047-b8e9-41f6-8448-f3042e87bfd1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_c2e7db00-d833-465d-a14f-462f33997d0a" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_8ca30047-b8e9-41f6-8448-f3042e87bfd1" xlink:to="loc_srt_ProductOrServiceAxis_c2e7db00-d833-465d-a14f-462f33997d0a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_c2e7db00-d833-465d-a14f-462f33997d0a_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_c2e7db00-d833-465d-a14f-462f33997d0a" xlink:to="loc_srt_ProductsAndServicesDomain_c2e7db00-d833-465d-a14f-462f33997d0a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_4eddc73c-eacc-4981-a919-3041a5703348" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_c2e7db00-d833-465d-a14f-462f33997d0a" xlink:to="loc_srt_ProductsAndServicesDomain_4eddc73c-eacc-4981-a919-3041a5703348" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_RentsMember_048f79e6-eb1c-49cc-ae94-473b21419beb" xlink:href="bdn-20230630.xsd#bdn_RentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_4eddc73c-eacc-4981-a919-3041a5703348" xlink:to="loc_bdn_RentsMember_048f79e6-eb1c-49cc-ae94-473b21419beb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_ThirdPartyManagementRevenueMember_d96bf2aa-b5a9-478f-9a79-1ae4320e216f" xlink:href="bdn-20230630.xsd#bdn_ThirdPartyManagementRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_4eddc73c-eacc-4981-a919-3041a5703348" xlink:to="loc_bdn_ThirdPartyManagementRevenueMember_d96bf2aa-b5a9-478f-9a79-1ae4320e216f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateOtherMember_24dc8e39-b23e-477e-9a25-0bb97d1047d6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_4eddc73c-eacc-4981-a919-3041a5703348" xlink:to="loc_us-gaap_RealEstateOtherMember_24dc8e39-b23e-477e-9a25-0bb97d1047d6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_c89499b2-a70b-4b08-a6c3-d99e80d64100" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_8ca30047-b8e9-41f6-8448-f3042e87bfd1" xlink:to="loc_srt_ConsolidatedEntitiesAxis_c89499b2-a70b-4b08-a6c3-d99e80d64100" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_c89499b2-a70b-4b08-a6c3-d99e80d64100_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_c89499b2-a70b-4b08-a6c3-d99e80d64100" xlink:to="loc_srt_ConsolidatedEntitiesDomain_c89499b2-a70b-4b08-a6c3-d99e80d64100_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_c10c88c0-874d-445e-b66a-41fa6082ad2d" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_c89499b2-a70b-4b08-a6c3-d99e80d64100" xlink:to="loc_srt_ConsolidatedEntitiesDomain_c10c88c0-874d-445e-b66a-41fa6082ad2d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember_5ac53a48-3104-45f6-b7fd-0d67c14513a0" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_c10c88c0-874d-445e-b66a-41fa6082ad2d" xlink:to="loc_srt_SubsidiariesMember_5ac53a48-3104-45f6-b7fd-0d67c14513a0" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMEBRANDYWINEOPERATINGPARTNERSHIPLP" xlink:type="simple" xlink:href="bdn-20230630.xsd#CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMEBRANDYWINEOPERATINGPARTNERSHIPLP"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMEBRANDYWINEOPERATINGPARTNERSHIPLP" xlink:type="extended" id="iee053b179fa44e73958005675d642ada_CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMEBRANDYWINEOPERATINGPARTNERSHIPLP">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_9a0169e5-92ae-4486-87b5-064de1b4ffb3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_4a5589ee-fbed-402b-8803-f95bd2569e39" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_9a0169e5-92ae-4486-87b5-064de1b4ffb3" xlink:to="loc_us-gaap_ProfitLoss_4a5589ee-fbed-402b-8803-f95bd2569e39" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_db95f158-0920-4782-afb5-bf15daaf5154" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_9a0169e5-92ae-4486-87b5-064de1b4ffb3" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_db95f158-0920-4782-afb5-bf15daaf5154" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseBeforeAdjustmentsAfterTax_73ef3cc5-ad8c-4273-98aa-01a9814b17ea" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseBeforeAdjustmentsAfterTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_db95f158-0920-4782-afb5-bf15daaf5154" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseBeforeAdjustmentsAfterTax_73ef3cc5-ad8c-4273-98aa-01a9814b17ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseAdjustmentsAfterTax_b8c9d715-54c1-44ba-b9a5-0c8abf5810ce" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseAdjustmentsAfterTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_db95f158-0920-4782-afb5-bf15daaf5154" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseAdjustmentsAfterTax_b8c9d715-54c1-44ba-b9a5-0c8abf5810ce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_06f9c16e-78f2-4098-9337-6804259a7d19" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_db95f158-0920-4782-afb5-bf15daaf5154" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_06f9c16e-78f2-4098-9337-6804259a7d19" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_e876540f-cab7-4b0b-880c-19d5d36a65ed" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_9a0169e5-92ae-4486-87b5-064de1b4ffb3" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_e876540f-cab7-4b0b-880c-19d5d36a65ed" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_8a616100-0986-4c9e-961c-a2fb5ea200b4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_9a0169e5-92ae-4486-87b5-064de1b4ffb3" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_8a616100-0986-4c9e-961c-a2fb5ea200b4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_ea7f0379-694b-4ad2-92af-d53dd3758726" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_9a0169e5-92ae-4486-87b5-064de1b4ffb3" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_ea7f0379-694b-4ad2-92af-d53dd3758726" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_8a805ec7-072e-4eb0-9f7a-c5fddc6a2ce2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_9a0169e5-92ae-4486-87b5-064de1b4ffb3" xlink:to="loc_us-gaap_StatementTable_8a805ec7-072e-4eb0-9f7a-c5fddc6a2ce2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_aa81f1bc-b173-4680-9237-f6fcb96610fd" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_8a805ec7-072e-4eb0-9f7a-c5fddc6a2ce2" xlink:to="loc_srt_ConsolidatedEntitiesAxis_aa81f1bc-b173-4680-9237-f6fcb96610fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_aa81f1bc-b173-4680-9237-f6fcb96610fd_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_aa81f1bc-b173-4680-9237-f6fcb96610fd" xlink:to="loc_srt_ConsolidatedEntitiesDomain_aa81f1bc-b173-4680-9237-f6fcb96610fd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_e932f5c7-d91c-4a8b-845e-ac0d0cb0d86a" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_aa81f1bc-b173-4680-9237-f6fcb96610fd" xlink:to="loc_srt_ConsolidatedEntitiesDomain_e932f5c7-d91c-4a8b-845e-ac0d0cb0d86a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember_95e716fc-a8a6-463d-b653-906384f0b940" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_e932f5c7-d91c-4a8b-845e-ac0d0cb0d86a" xlink:to="loc_srt_SubsidiariesMember_95e716fc-a8a6-463d-b653-906384f0b940" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/CONSOLIDATEDSTATEMENTSOFPARTNERSEQUITY" xlink:type="simple" xlink:href="bdn-20230630.xsd#CONSOLIDATEDSTATEMENTSOFPARTNERSEQUITY"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/CONSOLIDATEDSTATEMENTSOFPARTNERSEQUITY" xlink:type="extended" id="i567373cd3e444d4cac8bc66e4c39161c_CONSOLIDATEDSTATEMENTSOFPARTNERSEQUITY">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_5e4a4cf9-fb68-40f6-9066-b0e5e116719c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_0f24e845-cc4e-46ff-ac7f-62c3abea0bf3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInPartnersCapitalRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5e4a4cf9-fb68-40f6-9066-b0e5e116719c" xlink:to="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_0f24e845-cc4e-46ff-ac7f-62c3abea0bf3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesIssued_1a90f37a-9eae-4615-952d-764fed09e338" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_0f24e845-cc4e-46ff-ac7f-62c3abea0bf3" xlink:to="loc_us-gaap_SharesIssued_1a90f37a-9eae-4615-952d-764fed09e338" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_80591a27-ebae-4a79-b5e2-b1e6f362e300" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_0f24e845-cc4e-46ff-ac7f-62c3abea0bf3" xlink:to="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_80591a27-ebae-4a79-b5e2-b1e6f362e300" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_a40b83e5-f435-4542-b45f-376101ab9d84" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_0f24e845-cc4e-46ff-ac7f-62c3abea0bf3" xlink:to="loc_us-gaap_ProfitLoss_a40b83e5-f435-4542-b45f-376101ab9d84" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_e4510708-9333-4323-be90-8c57ea46f432" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_0f24e845-cc4e-46ff-ac7f-62c3abea0bf3" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_e4510708-9333-4323-be90-8c57ea46f432" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_ShareIssuanceFromToDeferredCompensationPlanShares_3d89b4ad-f09f-489c-9845-7aa135c3dce7" xlink:href="bdn-20230630.xsd#bdn_ShareIssuanceFromToDeferredCompensationPlanShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_0f24e845-cc4e-46ff-ac7f-62c3abea0bf3" xlink:to="loc_bdn_ShareIssuanceFromToDeferredCompensationPlanShares_3d89b4ad-f09f-489c-9845-7aa135c3dce7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_ShareIssuanceFromToDeferredCompensationPlan_3d0f9593-5928-4709-8f1e-940ab345c20d" xlink:href="bdn-20230630.xsd#bdn_ShareIssuanceFromToDeferredCompensationPlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_0f24e845-cc4e-46ff-ac7f-62c3abea0bf3" xlink:to="loc_bdn_ShareIssuanceFromToDeferredCompensationPlan_3d0f9593-5928-4709-8f1e-940ab345c20d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_PartnersCapitalAccountRepurchasedAndRetired_c2508f02-969b-4c40-807b-6cd411e6c576" xlink:href="bdn-20230630.xsd#bdn_PartnersCapitalAccountRepurchasedAndRetired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_0f24e845-cc4e-46ff-ac7f-62c3abea0bf3" xlink:to="loc_bdn_PartnersCapitalAccountRepurchasedAndRetired_c2508f02-969b-4c40-807b-6cd411e6c576" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuanceShares_43d63f7e-f3a3-4969-b8d7-d9a0191973b9" xlink:href="bdn-20230630.xsd#bdn_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuanceShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_0f24e845-cc4e-46ff-ac7f-62c3abea0bf3" xlink:to="loc_bdn_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuanceShares_43d63f7e-f3a3-4969-b8d7-d9a0191973b9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance_e87ebbcb-bed0-4cd8-8ddf-1ec90a0a2192" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_0f24e845-cc4e-46ff-ac7f-62c3abea0bf3" xlink:to="loc_us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance_e87ebbcb-bed0-4cd8-8ddf-1ec90a0a2192" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_55a9c581-a4c7-4dd7-a978-396049304b18" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_0f24e845-cc4e-46ff-ac7f-62c3abea0bf3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_55a9c581-a4c7-4dd7-a978-396049304b18" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_33eb0b2b-1ece-486f-bec5-c108d123f680" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_0f24e845-cc4e-46ff-ac7f-62c3abea0bf3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_33eb0b2b-1ece-486f-bec5-c108d123f680" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_AdjustmentIncreaseDecreaseOfRedeemablePartnershipUnitsToLiquidationValueAtPeriodEnd_4976af04-4730-48e9-98ca-f56b3a114e56" xlink:href="bdn-20230630.xsd#bdn_AdjustmentIncreaseDecreaseOfRedeemablePartnershipUnitsToLiquidationValueAtPeriodEnd"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_0f24e845-cc4e-46ff-ac7f-62c3abea0bf3" xlink:to="loc_bdn_AdjustmentIncreaseDecreaseOfRedeemablePartnershipUnitsToLiquidationValueAtPeriodEnd_4976af04-4730-48e9-98ca-f56b3a114e56" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountDistributions_fe70619c-e4bc-4d31-980c-45b26f8fb62a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapitalAccountDistributions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_0f24e845-cc4e-46ff-ac7f-62c3abea0bf3" xlink:to="loc_us-gaap_PartnersCapitalAccountDistributions_fe70619c-e4bc-4d31-980c-45b26f8fb62a" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesIssued_c94e2362-5f1c-4f96-be38-e3371adfdcff" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesIssued"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_39a23e24-e1ad-4a46-8ed4-df5d45eed996" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_3189093f-a4a3-40b6-bdeb-f65187477fdc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_5e4a4cf9-fb68-40f6-9066-b0e5e116719c" xlink:to="loc_us-gaap_StatementTable_3189093f-a4a3-40b6-bdeb-f65187477fdc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_c8aea8b0-a81c-4708-95dc-ae5b6e66ce99" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_3189093f-a4a3-40b6-bdeb-f65187477fdc" xlink:to="loc_srt_ConsolidatedEntitiesAxis_c8aea8b0-a81c-4708-95dc-ae5b6e66ce99" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_c8aea8b0-a81c-4708-95dc-ae5b6e66ce99_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_c8aea8b0-a81c-4708-95dc-ae5b6e66ce99" xlink:to="loc_srt_ConsolidatedEntitiesDomain_c8aea8b0-a81c-4708-95dc-ae5b6e66ce99_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_21373c6f-4d8e-43e4-b3ad-56a4b86bef12" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_c8aea8b0-a81c-4708-95dc-ae5b6e66ce99" xlink:to="loc_srt_ConsolidatedEntitiesDomain_21373c6f-4d8e-43e4-b3ad-56a4b86bef12" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember_462a3cf3-59e4-4961-b95d-3ddb5a50330b" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_21373c6f-4d8e-43e4-b3ad-56a4b86bef12" xlink:to="loc_srt_SubsidiariesMember_462a3cf3-59e4-4961-b95d-3ddb5a50330b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_fffd9789-6a0b-4213-ab16-1c8b80bdc9f3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_3189093f-a4a3-40b6-bdeb-f65187477fdc" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_fffd9789-6a0b-4213-ab16-1c8b80bdc9f3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_fffd9789-6a0b-4213-ab16-1c8b80bdc9f3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_fffd9789-6a0b-4213-ab16-1c8b80bdc9f3" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_fffd9789-6a0b-4213-ab16-1c8b80bdc9f3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_17b1fc01-72ad-4f27-8f81-ff09747fc880" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_fffd9789-6a0b-4213-ab16-1c8b80bdc9f3" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_17b1fc01-72ad-4f27-8f81-ff09747fc880" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralPartnerMember_0cb640c7-fad9-41d1-a868-7d29660a8f2e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralPartnerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_17b1fc01-72ad-4f27-8f81-ff09747fc880" xlink:to="loc_us-gaap_GeneralPartnerMember_0cb640c7-fad9-41d1-a868-7d29660a8f2e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_508e6fd4-d90e-4021-b07d-bdc964029ae2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_3189093f-a4a3-40b6-bdeb-f65187477fdc" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_508e6fd4-d90e-4021-b07d-bdc964029ae2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_508e6fd4-d90e-4021-b07d-bdc964029ae2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_508e6fd4-d90e-4021-b07d-bdc964029ae2" xlink:to="loc_us-gaap_EquityComponentDomain_508e6fd4-d90e-4021-b07d-bdc964029ae2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_5b742ee0-5887-44a6-9de7-97a48cccfa1e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_508e6fd4-d90e-4021-b07d-bdc964029ae2" xlink:to="loc_us-gaap_EquityComponentDomain_5b742ee0-5887-44a6-9de7-97a48cccfa1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_fa816056-cabf-4f4d-8959-0e99e078adf7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_5b742ee0-5887-44a6-9de7-97a48cccfa1e" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_fa816056-cabf-4f4d-8959-0e99e078adf7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_5de9ba4b-8c97-407f-9bdc-2c135ccc972b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_5b742ee0-5887-44a6-9de7-97a48cccfa1e" xlink:to="loc_us-gaap_NoncontrollingInterestMember_5de9ba4b-8c97-407f-9bdc-2c135ccc972b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/CONSOLIDATEDSTATEMENTSOFPARTNERSEQUITYParenthetical" xlink:type="simple" xlink:href="bdn-20230630.xsd#CONSOLIDATEDSTATEMENTSOFPARTNERSEQUITYParenthetical"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/CONSOLIDATEDSTATEMENTSOFPARTNERSEQUITYParenthetical" xlink:type="extended" id="i8a3f643155544b728017fb4ec0d5a745_CONSOLIDATEDSTATEMENTSOFPARTNERSEQUITYParenthetical">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_a4542a04-1635-47c9-9bd6-3ebe24738403" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DistributionsPerGeneralPartnershipUnitOutstanding_06bd760e-58ad-4f2e-a05e-d28da0b8c28e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DistributionsPerGeneralPartnershipUnitOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_a4542a04-1635-47c9-9bd6-3ebe24738403" xlink:to="loc_us-gaap_DistributionsPerGeneralPartnershipUnitOutstanding_06bd760e-58ad-4f2e-a05e-d28da0b8c28e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_d29aff44-a02a-4be3-9c05-a8a3171a7bab" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_a4542a04-1635-47c9-9bd6-3ebe24738403" xlink:to="loc_us-gaap_StatementTable_d29aff44-a02a-4be3-9c05-a8a3171a7bab" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_08a634aa-c1b6-474e-9854-71fd1ef45acd" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_d29aff44-a02a-4be3-9c05-a8a3171a7bab" xlink:to="loc_srt_ConsolidatedEntitiesAxis_08a634aa-c1b6-474e-9854-71fd1ef45acd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_08a634aa-c1b6-474e-9854-71fd1ef45acd_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_08a634aa-c1b6-474e-9854-71fd1ef45acd" xlink:to="loc_srt_ConsolidatedEntitiesDomain_08a634aa-c1b6-474e-9854-71fd1ef45acd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_4cf1d52f-5898-4ab6-a810-1c0f5cf9a1e5" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_08a634aa-c1b6-474e-9854-71fd1ef45acd" xlink:to="loc_srt_ConsolidatedEntitiesDomain_4cf1d52f-5898-4ab6-a810-1c0f5cf9a1e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember_2d66b8a9-0267-4435-ba83-4796a0c2363f" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_4cf1d52f-5898-4ab6-a810-1c0f5cf9a1e5" xlink:to="loc_srt_SubsidiariesMember_2d66b8a9-0267-4435-ba83-4796a0c2363f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_e71e08b7-56bd-4268-8cbb-6985a6a3b3d2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_d29aff44-a02a-4be3-9c05-a8a3171a7bab" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_e71e08b7-56bd-4268-8cbb-6985a6a3b3d2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_e71e08b7-56bd-4268-8cbb-6985a6a3b3d2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_e71e08b7-56bd-4268-8cbb-6985a6a3b3d2" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_e71e08b7-56bd-4268-8cbb-6985a6a3b3d2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_c36759e5-3a4e-44d6-9333-71a6d3968469" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_e71e08b7-56bd-4268-8cbb-6985a6a3b3d2" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_c36759e5-3a4e-44d6-9333-71a6d3968469" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralPartnerMember_60293649-3812-4e68-ab3d-a4f5a53446b8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralPartnerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_c36759e5-3a4e-44d6-9333-71a6d3968469" xlink:to="loc_us-gaap_GeneralPartnerMember_60293649-3812-4e68-ab3d-a4f5a53446b8" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWSBRANDYWINEOPERATINGPARTNERSHIPLP" xlink:type="simple" xlink:href="bdn-20230630.xsd#CONSOLIDATEDSTATEMENTSOFCASHFLOWSBRANDYWINEOPERATINGPARTNERSHIPLP"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWSBRANDYWINEOPERATINGPARTNERSHIPLP" xlink:type="extended" id="i1e716d04afee4461b47c4a0dc6d85f17_CONSOLIDATEDSTATEMENTSOFCASHFLOWSBRANDYWINEOPERATINGPARTNERSHIPLP">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_d9921902-c401-4d36-84f8-755606198f12" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_78402c8f-816f-441d-ab96-6e22455c22b1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_d9921902-c401-4d36-84f8-755606198f12" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_78402c8f-816f-441d-ab96-6e22455c22b1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_0217ffbc-f0f4-4c8f-98b4-f06adef407c6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_78402c8f-816f-441d-ab96-6e22455c22b1" xlink:to="loc_us-gaap_ProfitLoss_0217ffbc-f0f4-4c8f-98b4-f06adef407c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3cb53582-c65d-4dc4-b9bf-4bc74e034789" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_78402c8f-816f-441d-ab96-6e22455c22b1" xlink:to="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3cb53582-c65d-4dc4-b9bf-4bc74e034789" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_642917af-004a-49ee-98f5-e25534cfc934" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3cb53582-c65d-4dc4-b9bf-4bc74e034789" xlink:to="loc_us-gaap_DepreciationAndAmortization_642917af-004a-49ee-98f5-e25534cfc934" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_8ba04473-b6b4-4445-b4cf-7f0e6e10303c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3cb53582-c65d-4dc4-b9bf-4bc74e034789" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_8ba04473-b6b4-4445-b4cf-7f0e6e10303c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfDebtDiscountPremium_bccafb41-903c-4dd9-a037-94a800ccc1ea" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfDebtDiscountPremium"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3cb53582-c65d-4dc4-b9bf-4bc74e034789" xlink:to="loc_us-gaap_AmortizationOfDebtDiscountPremium_bccafb41-903c-4dd9-a037-94a800ccc1ea" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_48d79e3c-63c6-4aa9-b030-7e86e74fd260" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3cb53582-c65d-4dc4-b9bf-4bc74e034789" xlink:to="loc_us-gaap_ShareBasedCompensation_48d79e3c-63c6-4aa9-b030-7e86e74fd260" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_StraightLineRentExcludingRentTerminationFee_6dc9eaf4-9f25-43f1-9ced-a9349abd1f62" xlink:href="bdn-20230630.xsd#bdn_StraightLineRentExcludingRentTerminationFee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3cb53582-c65d-4dc4-b9bf-4bc74e034789" xlink:to="loc_bdn_StraightLineRentExcludingRentTerminationFee_6dc9eaf4-9f25-43f1-9ced-a9349abd1f62" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfAboveAndBelowMarketLeases_f9bdb5f1-f321-40aa-af66-ef4c1adaeb38" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfAboveAndBelowMarketLeases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3cb53582-c65d-4dc4-b9bf-4bc74e034789" xlink:to="loc_us-gaap_AmortizationOfAboveAndBelowMarketLeases_f9bdb5f1-f321-40aa-af66-ef4c1adaeb38" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_StraightLineGroundRentExpense_0d5536ae-5efc-4c99-9edd-4fda934f9af5" xlink:href="bdn-20230630.xsd#bdn_StraightLineGroundRentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3cb53582-c65d-4dc4-b9bf-4bc74e034789" xlink:to="loc_bdn_StraightLineGroundRentExpense_0d5536ae-5efc-4c99-9edd-4fda934f9af5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_NetGainLossOnRealEstateVentureTransactions_708e8b9e-6d9e-4ddd-9e7f-4b4b14628231" xlink:href="bdn-20230630.xsd#bdn_NetGainLossOnRealEstateVentureTransactions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3cb53582-c65d-4dc4-b9bf-4bc74e034789" xlink:to="loc_bdn_NetGainLossOnRealEstateVentureTransactions_708e8b9e-6d9e-4ddd-9e7f-4b4b14628231" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfProperties_ef3a6ba1-2dd4-46bb-a309-1eb86858e036" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnSaleOfProperties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3cb53582-c65d-4dc4-b9bf-4bc74e034789" xlink:to="loc_us-gaap_GainLossOnSaleOfProperties_ef3a6ba1-2dd4-46bb-a309-1eb86858e036" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetImpairmentCharges_a90f3557-a57a-478c-a749-d25e6edd12b3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3cb53582-c65d-4dc4-b9bf-4bc74e034789" xlink:to="loc_us-gaap_AssetImpairmentCharges_a90f3557-a57a-478c-a749-d25e6edd12b3" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_IncomeLossFromRealEstateVenturesNetOfDistributions_c4a3dc47-c26b-41fd-bbb1-51a2a1e1e3e3" xlink:href="bdn-20230630.xsd#bdn_IncomeLossFromRealEstateVenturesNetOfDistributions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3cb53582-c65d-4dc4-b9bf-4bc74e034789" xlink:to="loc_bdn_IncomeLossFromRealEstateVenturesNetOfDistributions_c4a3dc47-c26b-41fd-bbb1-51a2a1e1e3e3" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_6da394b4-0307-48ca-95f8-ad9a7e07ffe4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3cb53582-c65d-4dc4-b9bf-4bc74e034789" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_6da394b4-0307-48ca-95f8-ad9a7e07ffe4" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_4d10bef6-695a-420a-8ec6-15faa232f559" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3cb53582-c65d-4dc4-b9bf-4bc74e034789" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_4d10bef6-695a-420a-8ec6-15faa232f559" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_f8cad115-08e9-486c-bc4f-e9dfc842d240" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_4d10bef6-695a-420a-8ec6-15faa232f559" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_f8cad115-08e9-486c-bc4f-e9dfc842d240" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_b9062d49-4c91-4fc2-b3a7-776c3b869710" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_4d10bef6-695a-420a-8ec6-15faa232f559" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_b9062d49-4c91-4fc2-b3a7-776c3b869710" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_5bc1079d-a5cd-4007-a88e-947c9919114e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_4d10bef6-695a-420a-8ec6-15faa232f559" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_5bc1079d-a5cd-4007-a88e-947c9919114e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_7a93c12b-a499-4cab-8ddd-85c18e834fff" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_4d10bef6-695a-420a-8ec6-15faa232f559" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_7a93c12b-a499-4cab-8ddd-85c18e834fff" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_7eaf75cb-b848-41c4-834e-79176f0d4417" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_4d10bef6-695a-420a-8ec6-15faa232f559" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_7eaf75cb-b848-41c4-834e-79176f0d4417" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_a50254c8-8168-4bbc-8bc7-166a2c01a183" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_78402c8f-816f-441d-ab96-6e22455c22b1" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_a50254c8-8168-4bbc-8bc7-166a2c01a183" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ca40904-d9e4-4cb0-80d3-8fd83124954a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_d9921902-c401-4d36-84f8-755606198f12" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ca40904-d9e4-4cb0-80d3-8fd83124954a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireRealEstate_6a702bfb-fec8-478f-b703-ce9280e76414" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsToAcquireRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ca40904-d9e4-4cb0-80d3-8fd83124954a" xlink:to="loc_us-gaap_PaymentsToAcquireRealEstate_6a702bfb-fec8-478f-b703-ce9280e76414" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_0fda7aac-967d-4cd5-9e21-8f334db1c537" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ca40904-d9e4-4cb0-80d3-8fd83124954a" xlink:to="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_0fda7aac-967d-4cd5-9e21-8f334db1c537" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForTenantImprovements_e52f6b4a-35a5-438d-8415-4fd9afecdf0c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForTenantImprovements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ca40904-d9e4-4cb0-80d3-8fd83124954a" xlink:to="loc_us-gaap_PaymentsForTenantImprovements_e52f6b4a-35a5-438d-8415-4fd9afecdf0c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_PaymentsToRedevelopRealEstate_a61a6fd8-7f10-4d78-922e-0e2123ae6f3b" xlink:href="bdn-20230630.xsd#bdn_PaymentsToRedevelopRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ca40904-d9e4-4cb0-80d3-8fd83124954a" xlink:to="loc_bdn_PaymentsToRedevelopRealEstate_a61a6fd8-7f10-4d78-922e-0e2123ae6f3b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToDevelopRealEstateAssets_92057356-7b8e-48a4-b5b7-79caadeddceb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsToDevelopRealEstateAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ca40904-d9e4-4cb0-80d3-8fd83124954a" xlink:to="loc_us-gaap_PaymentsToDevelopRealEstateAssets_92057356-7b8e-48a4-b5b7-79caadeddceb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_AdvancesToTenantForPurchaseOfTenantAssetsNetOfRepayments_9f58e6ad-c7b4-49bd-a0ae-d8ed14900247" xlink:href="bdn-20230630.xsd#bdn_AdvancesToTenantForPurchaseOfTenantAssetsNetOfRepayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ca40904-d9e4-4cb0-80d3-8fd83124954a" xlink:to="loc_bdn_AdvancesToTenantForPurchaseOfTenantAssetsNetOfRepayments_9f58e6ad-c7b4-49bd-a0ae-d8ed14900247" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_05be40c4-4dda-4177-9412-ecf2255f54c9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsToAcquireEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ca40904-d9e4-4cb0-80d3-8fd83124954a" xlink:to="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_05be40c4-4dda-4177-9412-ecf2255f54c9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForProceedsFromDepositsOnRealEstateAcquisitions_34c8d573-52fc-446e-a599-d5b8ae21e322" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForProceedsFromDepositsOnRealEstateAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ca40904-d9e4-4cb0-80d3-8fd83124954a" xlink:to="loc_us-gaap_PaymentsForProceedsFromDepositsOnRealEstateAcquisitions_34c8d573-52fc-446e-a599-d5b8ae21e322" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital_729b8f27-d161-415a-86db-b9ba69d4fe35" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ca40904-d9e4-4cb0-80d3-8fd83124954a" xlink:to="loc_us-gaap_ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital_729b8f27-d161-415a-86db-b9ba69d4fe35" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForLeasingCosts_17c8af6b-61ec-4511-99cd-178b8d315519" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForLeasingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ca40904-d9e4-4cb0-80d3-8fd83124954a" xlink:to="loc_us-gaap_PaymentsForLeasingCosts_17c8af6b-61ec-4511-99cd-178b8d315519" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_47e4e672-b54f-4481-87db-2242fb9c81ab" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ca40904-d9e4-4cb0-80d3-8fd83124954a" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_47e4e672-b54f-4481-87db-2242fb9c81ab" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_e2bd6332-3a7c-4bf1-b157-a8e3c61aa64d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_d9921902-c401-4d36-84f8-755606198f12" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_e2bd6332-3a7c-4bf1-b157-a8e3c61aa64d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_c89cce81-c10f-4f06-972b-4086a26ffc5a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_e2bd6332-3a7c-4bf1-b157-a8e3c61aa64d" xlink:to="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_c89cce81-c10f-4f06-972b-4086a26ffc5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_8de231f1-d20f-4130-9d29-46c9d1d1259a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RepaymentsOfLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_e2bd6332-3a7c-4bf1-b157-a8e3c61aa64d" xlink:to="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_8de231f1-d20f-4130-9d29-46c9d1d1259a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfUnsecuredDebt_f98e3124-137d-4ae5-bb3a-258b41052564" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RepaymentsOfUnsecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_e2bd6332-3a7c-4bf1-b157-a8e3c61aa64d" xlink:to="loc_us-gaap_RepaymentsOfUnsecuredDebt_f98e3124-137d-4ae5-bb3a-258b41052564" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromUnsecuredNotesPayable_a43c56f3-7809-40ba-ba56-9993da6c27d7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromUnsecuredNotesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_e2bd6332-3a7c-4bf1-b157-a8e3c61aa64d" xlink:to="loc_us-gaap_ProceedsFromUnsecuredNotesPayable_a43c56f3-7809-40ba-ba56-9993da6c27d7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSecuredNotesPayable_e6eee7d1-f501-4ad4-90a2-17d277a21a4c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromSecuredNotesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_e2bd6332-3a7c-4bf1-b157-a8e3c61aa64d" xlink:to="loc_us-gaap_ProceedsFromSecuredNotesPayable_e6eee7d1-f501-4ad4-90a2-17d277a21a4c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfFinancingCosts_90bcde75-ad5f-40a1-beda-20f263ba1ca5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_e2bd6332-3a7c-4bf1-b157-a8e3c61aa64d" xlink:to="loc_us-gaap_PaymentsOfFinancingCosts_90bcde75-ad5f-40a1-beda-20f263ba1ca5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_PaymentsOnAccountOfEmployeeTaxWithholdingsOnShareBasedAwards_f590a7a4-002b-4c7d-9c03-1b23cebeaf92" xlink:href="bdn-20230630.xsd#bdn_PaymentsOnAccountOfEmployeeTaxWithholdingsOnShareBasedAwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_e2bd6332-3a7c-4bf1-b157-a8e3c61aa64d" xlink:to="loc_bdn_PaymentsOnAccountOfEmployeeTaxWithholdingsOnShareBasedAwards_f590a7a4-002b-4c7d-9c03-1b23cebeaf92" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_RepurchaseOfRedeemableUnits_d2b9650c-e6e4-4bc2-8147-7b33485b675e" xlink:href="bdn-20230630.xsd#bdn_RepurchaseOfRedeemableUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_e2bd6332-3a7c-4bf1-b157-a8e3c61aa64d" xlink:to="loc_bdn_RepurchaseOfRedeemableUnits_d2b9650c-e6e4-4bc2-8147-7b33485b675e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_PaymentOfOrdinaryDividendsCommonStockAndPreferredStock_ca992916-2516-4abe-83c4-f82ef18098ee" xlink:href="bdn-20230630.xsd#bdn_PaymentOfOrdinaryDividendsCommonStockAndPreferredStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_e2bd6332-3a7c-4bf1-b157-a8e3c61aa64d" xlink:to="loc_bdn_PaymentOfOrdinaryDividendsCommonStockAndPreferredStock_ca992916-2516-4abe-83c4-f82ef18098ee" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_c1846df2-b095-43a5-852a-88021dd0d2ba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_e2bd6332-3a7c-4bf1-b157-a8e3c61aa64d" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_c1846df2-b095-43a5-852a-88021dd0d2ba" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_eb2166a2-73e9-42da-b36f-d4aa09e0c50d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_d9921902-c401-4d36-84f8-755606198f12" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_eb2166a2-73e9-42da-b36f-d4aa09e0c50d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_6a4296c8-808a-4d43-b96d-eab8bebb4802" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_d9921902-c401-4d36-84f8-755606198f12" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_6a4296c8-808a-4d43-b96d-eab8bebb4802" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_00324903-5d69-4efe-8660-479955f25b33" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_ReconciliationOfCashCashEquivalentsAndRestrictedCashAbstract_bd2450b7-3301-4d75-a9b2-e7107952f4ff" xlink:href="bdn-20230630.xsd#bdn_ReconciliationOfCashCashEquivalentsAndRestrictedCashAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_d9921902-c401-4d36-84f8-755606198f12" xlink:to="loc_bdn_ReconciliationOfCashCashEquivalentsAndRestrictedCashAbstract_bd2450b7-3301-4d75-a9b2-e7107952f4ff" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_084f21dc-6eab-4d48-9c17-d82df87f2341" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_ReconciliationOfCashCashEquivalentsAndRestrictedCashAbstract_bd2450b7-3301-4d75-a9b2-e7107952f4ff" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_084f21dc-6eab-4d48-9c17-d82df87f2341" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalents_a6ed3979-10ac-4b84-a61c-7081b50f9d33" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_ReconciliationOfCashCashEquivalentsAndRestrictedCashAbstract_bd2450b7-3301-4d75-a9b2-e7107952f4ff" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalents_a6ed3979-10ac-4b84-a61c-7081b50f9d33" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_17124544-d708-4df7-9766-8630ef839025" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_4cbafdec-62b4-4b28-beca-f6a3a98e3b79" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalents_86607c6a-e28c-4463-8557-a3b54d4fe9bb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_c2cc7e68-3b70-42c2-94e6-38e4fce45692" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_a12ab403-802b-40a0-83d0-b2484b4d0f5e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_d9921902-c401-4d36-84f8-755606198f12" xlink:to="loc_us-gaap_SupplementalCashFlowInformationAbstract_a12ab403-802b-40a0-83d0-b2484b4d0f5e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPaidNet_f945029b-42e2-4e9a-9871-2b79854ba176" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestPaidNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_a12ab403-802b-40a0-83d0-b2484b4d0f5e" xlink:to="loc_us-gaap_InterestPaidNet_f945029b-42e2-4e9a-9871-2b79854ba176" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesPaidNet_dde617eb-8b47-4de2-a3e9-505f8e832943" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxesPaidNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_a12ab403-802b-40a0-83d0-b2484b4d0f5e" xlink:to="loc_us-gaap_IncomeTaxesPaidNet_dde617eb-8b47-4de2-a3e9-505f8e832943" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_c1dcb96f-7267-41de-8e1f-e49e1a072831" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_d9921902-c401-4d36-84f8-755606198f12" xlink:to="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_c1dcb96f-7267-41de-8e1f-e49e1a072831" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPayableCurrentAndNoncurrent_71c59554-c37a-4eb1-8404-eecdded38bb4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_c1dcb96f-7267-41de-8e1f-e49e1a072831" xlink:to="loc_us-gaap_DividendsPayableCurrentAndNoncurrent_71c59554-c37a-4eb1-8404-eecdded38bb4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_NoncashOrPartNoncashDispositionOfInvestingRealEstate_03d2311a-44b9-4308-b0b7-25b8b8b6ebda" xlink:href="bdn-20230630.xsd#bdn_NoncashOrPartNoncashDispositionOfInvestingRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_c1dcb96f-7267-41de-8e1f-e49e1a072831" xlink:to="loc_bdn_NoncashOrPartNoncashDispositionOfInvestingRealEstate_03d2311a-44b9-4308-b0b7-25b8b8b6ebda" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_NoncashOrPartNoncashDeconsolidationOperatingRealEstate_9d2bbd48-4dbf-48a8-b60c-ae124781b30c" xlink:href="bdn-20230630.xsd#bdn_NoncashOrPartNoncashDeconsolidationOperatingRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_c1dcb96f-7267-41de-8e1f-e49e1a072831" xlink:to="loc_bdn_NoncashOrPartNoncashDeconsolidationOperatingRealEstate_9d2bbd48-4dbf-48a8-b60c-ae124781b30c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_OtherNoncashInvestingAndFinancingActivitiesIncreaseDecreaseInOtherAssetsResultOfInvestingActivities_6c584348-4491-4198-9dc3-39a83155ba30" xlink:href="bdn-20230630.xsd#bdn_OtherNoncashInvestingAndFinancingActivitiesIncreaseDecreaseInOtherAssetsResultOfInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_c1dcb96f-7267-41de-8e1f-e49e1a072831" xlink:to="loc_bdn_OtherNoncashInvestingAndFinancingActivitiesIncreaseDecreaseInOtherAssetsResultOfInvestingActivities_6c584348-4491-4198-9dc3-39a83155ba30" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_ChangeInCapitalExpendituresFinancedThroughAccountsPayable_ee977b60-ef46-4522-a03f-046f9d08c2bc" xlink:href="bdn-20230630.xsd#bdn_ChangeInCapitalExpendituresFinancedThroughAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_c1dcb96f-7267-41de-8e1f-e49e1a072831" xlink:to="loc_bdn_ChangeInCapitalExpendituresFinancedThroughAccountsPayable_ee977b60-ef46-4522-a03f-046f9d08c2bc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_ChangeInCapitalExpendituresFinancedThroughRetentionPayableAtPeriodEnd_68d44a41-9608-4df8-bd89-e316902d30d3" xlink:href="bdn-20230630.xsd#bdn_ChangeInCapitalExpendituresFinancedThroughRetentionPayableAtPeriodEnd"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_c1dcb96f-7267-41de-8e1f-e49e1a072831" xlink:to="loc_bdn_ChangeInCapitalExpendituresFinancedThroughRetentionPayableAtPeriodEnd_68d44a41-9608-4df8-bd89-e316902d30d3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_161cbb53-041a-4d1e-9538-db189a6b4aae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_d9921902-c401-4d36-84f8-755606198f12" xlink:to="loc_us-gaap_StatementTable_161cbb53-041a-4d1e-9538-db189a6b4aae" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_ac9b247c-da54-420e-973d-fe1a310c5914" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_161cbb53-041a-4d1e-9538-db189a6b4aae" xlink:to="loc_srt_ConsolidatedEntitiesAxis_ac9b247c-da54-420e-973d-fe1a310c5914" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_ac9b247c-da54-420e-973d-fe1a310c5914_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_ac9b247c-da54-420e-973d-fe1a310c5914" xlink:to="loc_srt_ConsolidatedEntitiesDomain_ac9b247c-da54-420e-973d-fe1a310c5914_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_e7b64404-ef20-410c-986e-546e3dd6de8b" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_ac9b247c-da54-420e-973d-fe1a310c5914" xlink:to="loc_srt_ConsolidatedEntitiesDomain_e7b64404-ef20-410c-986e-546e3dd6de8b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember_73703e1d-d63a-49dc-95bf-59158003e28f" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_e7b64404-ef20-410c-986e-546e3dd6de8b" xlink:to="loc_srt_SubsidiariesMember_73703e1d-d63a-49dc-95bf-59158003e28f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWSBRANDYWINEOPERATINGPARTNERSHIPLPParenthetical" xlink:type="simple" xlink:href="bdn-20230630.xsd#CONSOLIDATEDSTATEMENTSOFCASHFLOWSBRANDYWINEOPERATINGPARTNERSHIPLPParenthetical"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWSBRANDYWINEOPERATINGPARTNERSHIPLPParenthetical" xlink:type="extended" id="i36745b58e7054dee8b6d8042a65c0a65_CONSOLIDATEDSTATEMENTSOFCASHFLOWSBRANDYWINEOPERATINGPARTNERSHIPLPParenthetical">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_c01385fd-3985-4ced-9fef-e950a3c091b0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPaidCapitalized_ca9efa01-d8ba-4801-8bb5-dc6230b5258a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestPaidCapitalized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c01385fd-3985-4ced-9fef-e950a3c091b0" xlink:to="loc_us-gaap_InterestPaidCapitalized_ca9efa01-d8ba-4801-8bb5-dc6230b5258a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_ade5b158-7bad-46f0-8dfb-40795c186b67" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_c01385fd-3985-4ced-9fef-e950a3c091b0" xlink:to="loc_us-gaap_StatementTable_ade5b158-7bad-46f0-8dfb-40795c186b67" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_a71fea21-f53b-4e96-bc72-9ef5eac5f68e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_ade5b158-7bad-46f0-8dfb-40795c186b67" xlink:to="loc_srt_ConsolidatedEntitiesAxis_a71fea21-f53b-4e96-bc72-9ef5eac5f68e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_a71fea21-f53b-4e96-bc72-9ef5eac5f68e_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_a71fea21-f53b-4e96-bc72-9ef5eac5f68e" xlink:to="loc_srt_ConsolidatedEntitiesDomain_a71fea21-f53b-4e96-bc72-9ef5eac5f68e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_34691462-6993-41a7-b6b6-cfe244ac123e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_a71fea21-f53b-4e96-bc72-9ef5eac5f68e" xlink:to="loc_srt_ConsolidatedEntitiesDomain_34691462-6993-41a7-b6b6-cfe244ac123e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember_b86da778-7eaa-47f9-b04b-44ce2bf02492" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_34691462-6993-41a7-b6b6-cfe244ac123e" xlink:to="loc_srt_SubsidiariesMember_b86da778-7eaa-47f9-b04b-44ce2bf02492" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/ORGANIZATIONOFTHEPARENTCOMPANYANDTHEOPERATINGPARTNERSHIPNarrativeDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#ORGANIZATIONOFTHEPARENTCOMPANYANDTHEOPERATINGPARTNERSHIPNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/ORGANIZATIONOFTHEPARENTCOMPANYANDTHEOPERATINGPARTNERSHIPNarrativeDetails" xlink:type="extended" id="if5d6fa5c537e464fa9c00f2206968ee9_ORGANIZATIONOFTHEPARENTCOMPANYANDTHEOPERATINGPARTNERSHIPNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipLineItems_284131ab-f6fb-461e-9f47-454e946ec7a2" xlink:href="bdn-20230630.xsd#bdn_OrganizationOfParentCompanyAndOperatingPartnershipLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_fde00fa0-0c94-47ec-872e-b9cfe7fa6837" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MinorityInterestOwnershipPercentageByParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipLineItems_284131ab-f6fb-461e-9f47-454e946ec7a2" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_fde00fa0-0c94-47ec-872e-b9cfe7fa6837" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfRealEstateProperties_774ec9d2-e302-4a57-9113-22dda49dcb44" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NumberOfRealEstateProperties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipLineItems_284131ab-f6fb-461e-9f47-454e946ec7a2" xlink:to="loc_us-gaap_NumberOfRealEstateProperties_774ec9d2-e302-4a57-9113-22dda49dcb44" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AreaOfRealEstateProperty_09b64aca-3dea-4f16-baa7-cf2520adc842" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AreaOfRealEstateProperty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipLineItems_284131ab-f6fb-461e-9f47-454e946ec7a2" xlink:to="loc_us-gaap_AreaOfRealEstateProperty_09b64aca-3dea-4f16-baa7-cf2520adc842" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_AreaOfLandHeldForDevelopment_caeca884-6d39-4e64-bd00-ca567d79539a" xlink:href="bdn-20230630.xsd#bdn_AreaOfLandHeldForDevelopment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipLineItems_284131ab-f6fb-461e-9f47-454e946ec7a2" xlink:to="loc_bdn_AreaOfLandHeldForDevelopment_caeca884-6d39-4e64-bd00-ca567d79539a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_NumberOfParcelsOfLand_4c3682f5-75e5-4c63-b863-304b6aa99f46" xlink:href="bdn-20230630.xsd#bdn_NumberOfParcelsOfLand"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipLineItems_284131ab-f6fb-461e-9f47-454e946ec7a2" xlink:to="loc_bdn_NumberOfParcelsOfLand_4c3682f5-75e5-4c63-b863-304b6aa99f46" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_LeaseAgreementTerm_3383b281-a7c7-4b14-83bf-089495786eae" xlink:href="bdn-20230630.xsd#bdn_LeaseAgreementTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipLineItems_284131ab-f6fb-461e-9f47-454e946ec7a2" xlink:to="loc_bdn_LeaseAgreementTerm_3383b281-a7c7-4b14-83bf-089495786eae" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_AreaOfAdditionalUndevelopedParcelsOfLandWithOptionToPurchase_8eb773fc-a141-4f6e-bc9b-614401e0d5b9" xlink:href="bdn-20230630.xsd#bdn_AreaOfAdditionalUndevelopedParcelsOfLandWithOptionToPurchase"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipLineItems_284131ab-f6fb-461e-9f47-454e946ec7a2" xlink:to="loc_bdn_AreaOfAdditionalUndevelopedParcelsOfLandWithOptionToPurchase_8eb773fc-a141-4f6e-bc9b-614401e0d5b9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipTable_5a5660b2-0cb4-48fb-b294-ef8c0a6610a3" xlink:href="bdn-20230630.xsd#bdn_OrganizationOfParentCompanyAndOperatingPartnershipTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipLineItems_284131ab-f6fb-461e-9f47-454e946ec7a2" xlink:to="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipTable_5a5660b2-0cb4-48fb-b294-ef8c0a6610a3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_15d05e9c-0cf2-45d2-8358-1af66b7ccf64" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipTable_5a5660b2-0cb4-48fb-b294-ef8c0a6610a3" xlink:to="loc_srt_OwnershipAxis_15d05e9c-0cf2-45d2-8358-1af66b7ccf64" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_15d05e9c-0cf2-45d2-8358-1af66b7ccf64_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_15d05e9c-0cf2-45d2-8358-1af66b7ccf64" xlink:to="loc_srt_OwnershipDomain_15d05e9c-0cf2-45d2-8358-1af66b7ccf64_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_8efac95c-d4f0-44db-b04a-b8f59771dd01" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_15d05e9c-0cf2-45d2-8358-1af66b7ccf64" xlink:to="loc_srt_OwnershipDomain_8efac95c-d4f0-44db-b04a-b8f59771dd01" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_BrandywineOperatingPartnershipLPMember_dc3f2fac-0ace-4b31-a05c-7525974a1ec8" xlink:href="bdn-20230630.xsd#bdn_BrandywineOperatingPartnershipLPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_8efac95c-d4f0-44db-b04a-b8f59771dd01" xlink:to="loc_bdn_BrandywineOperatingPartnershipLPMember_dc3f2fac-0ace-4b31-a05c-7525974a1ec8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_78087330-7df1-46ca-b89a-c39b6d42b3ed" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipTable_5a5660b2-0cb4-48fb-b294-ef8c0a6610a3" xlink:to="loc_srt_ConsolidatedEntitiesAxis_78087330-7df1-46ca-b89a-c39b6d42b3ed" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_78087330-7df1-46ca-b89a-c39b6d42b3ed_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_78087330-7df1-46ca-b89a-c39b6d42b3ed" xlink:to="loc_srt_ConsolidatedEntitiesDomain_78087330-7df1-46ca-b89a-c39b6d42b3ed_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_559e6227-0ab2-49c1-879c-802a5806786c" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_78087330-7df1-46ca-b89a-c39b6d42b3ed" xlink:to="loc_srt_ConsolidatedEntitiesDomain_559e6227-0ab2-49c1-879c-802a5806786c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ParentCompanyMember_42c78d19-6878-4aad-a35f-d7af12042c18" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ParentCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_559e6227-0ab2-49c1-879c-802a5806786c" xlink:to="loc_srt_ParentCompanyMember_42c78d19-6878-4aad-a35f-d7af12042c18" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_ManagementCompanySubsidiariesMember_e48ae305-af3a-4290-b108-212097943071" xlink:href="bdn-20230630.xsd#bdn_ManagementCompanySubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_559e6227-0ab2-49c1-879c-802a5806786c" xlink:to="loc_bdn_ManagementCompanySubsidiariesMember_e48ae305-af3a-4290-b108-212097943071" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_b93bc6ca-401f-4fcd-8c30-8d8717b8b8bf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipTable_5a5660b2-0cb4-48fb-b294-ef8c0a6610a3" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_b93bc6ca-401f-4fcd-8c30-8d8717b8b8bf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b93bc6ca-401f-4fcd-8c30-8d8717b8b8bf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_b93bc6ca-401f-4fcd-8c30-8d8717b8b8bf" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b93bc6ca-401f-4fcd-8c30-8d8717b8b8bf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a26ddb08-c712-4a6d-9fe3-735b5ceaf49b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_b93bc6ca-401f-4fcd-8c30-8d8717b8b8bf" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a26ddb08-c712-4a6d-9fe3-735b5ceaf49b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_LeasholdInterestLandMember_e907d2b8-89f3-46de-8616-ccf6f21c538d" xlink:href="bdn-20230630.xsd#bdn_LeasholdInterestLandMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a26ddb08-c712-4a6d-9fe3-735b5ceaf49b" xlink:to="loc_bdn_LeasholdInterestLandMember_e907d2b8-89f3-46de-8616-ccf6f21c538d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnconsolidatedPropertiesMember_8ae3aa3b-a5af-4b90-ae26-cb234e940b2b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnconsolidatedPropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a26ddb08-c712-4a6d-9fe3-735b5ceaf49b" xlink:to="loc_us-gaap_UnconsolidatedPropertiesMember_8ae3aa3b-a5af-4b90-ae26-cb234e940b2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_ad79a7c7-b030-4897-9f41-f4674ec3978b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipTable_5a5660b2-0cb4-48fb-b294-ef8c0a6610a3" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_ad79a7c7-b030-4897-9f41-f4674ec3978b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_ad79a7c7-b030-4897-9f41-f4674ec3978b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_ad79a7c7-b030-4897-9f41-f4674ec3978b" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_ad79a7c7-b030-4897-9f41-f4674ec3978b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_8a3af491-ae94-406a-8d13-f5fed7988a9b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_ad79a7c7-b030-4897-9f41-f4674ec3978b" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_8a3af491-ae94-406a-8d13-f5fed7988a9b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_LandParcelOneMember_cea7e6d4-91b7-45f2-9a00-6daaad9d2038" xlink:href="bdn-20230630.xsd#bdn_LandParcelOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_8a3af491-ae94-406a-8d13-f5fed7988a9b" xlink:to="loc_bdn_LandParcelOneMember_cea7e6d4-91b7-45f2-9a00-6daaad9d2038" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_04e3bb22-053f-48cb-8130-8ceab357f456" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipTable_5a5660b2-0cb4-48fb-b294-ef8c0a6610a3" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_04e3bb22-053f-48cb-8130-8ceab357f456" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_04e3bb22-053f-48cb-8130-8ceab357f456_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_04e3bb22-053f-48cb-8130-8ceab357f456" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_04e3bb22-053f-48cb-8130-8ceab357f456_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_612afffb-1710-42d5-9f4f-f82c35f9fe88" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_04e3bb22-053f-48cb-8130-8ceab357f456" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_612afffb-1710-42d5-9f4f-f82c35f9fe88" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_UnconsolidatedRealEstateVenturesMember_fd983c32-e069-486b-909d-74bc0fc21b21" xlink:href="bdn-20230630.xsd#bdn_UnconsolidatedRealEstateVenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_612afffb-1710-42d5-9f4f-f82c35f9fe88" xlink:to="loc_bdn_UnconsolidatedRealEstateVenturesMember_fd983c32-e069-486b-909d-74bc0fc21b21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesAxis_6297c4f5-6246-45b8-8855-e73507798e90" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstatePropertiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bdn_OrganizationOfParentCompanyAndOperatingPartnershipTable_5a5660b2-0cb4-48fb-b294-ef8c0a6610a3" xlink:to="loc_us-gaap_RealEstatePropertiesAxis_6297c4f5-6246-45b8-8855-e73507798e90" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_6297c4f5-6246-45b8-8855-e73507798e90_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_6297c4f5-6246-45b8-8855-e73507798e90" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_6297c4f5-6246-45b8-8855-e73507798e90_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_53a1375e-952e-49b2-a775-9d585da9a0d7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_6297c4f5-6246-45b8-8855-e73507798e90" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_53a1375e-952e-49b2-a775-9d585da9a0d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WhollyOwnedPropertiesMember_8ea5d88b-b66f-4fa5-a3fc-2206018ae6b2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WhollyOwnedPropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesDomain_53a1375e-952e-49b2-a775-9d585da9a0d7" xlink:to="loc_us-gaap_WhollyOwnedPropertiesMember_8ea5d88b-b66f-4fa5-a3fc-2206018ae6b2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartiallyOwnedPropertiesMember_0df2e557-6ef1-44dd-b1d9-6534b5e1d501" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartiallyOwnedPropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesDomain_53a1375e-952e-49b2-a775-9d585da9a0d7" xlink:to="loc_us-gaap_PartiallyOwnedPropertiesMember_0df2e557-6ef1-44dd-b1d9-6534b5e1d501" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/ORGANIZATIONOFTHEPARENTCOMPANYANDTHEOPERATINGPARTNERSHIPSummaryofCorePortfolioofOperatingPropertiesandExcludesDevelopmentRedevelopmentandHeldforSaleDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#ORGANIZATIONOFTHEPARENTCOMPANYANDTHEOPERATINGPARTNERSHIPSummaryofCorePortfolioofOperatingPropertiesandExcludesDevelopmentRedevelopmentandHeldforSaleDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/ORGANIZATIONOFTHEPARENTCOMPANYANDTHEOPERATINGPARTNERSHIPSummaryofCorePortfolioofOperatingPropertiesandExcludesDevelopmentRedevelopmentandHeldforSaleDetails" xlink:type="extended" id="i41efed378d3641639615ad4ef7991607_ORGANIZATIONOFTHEPARENTCOMPANYANDTHEOPERATINGPARTNERSHIPSummaryofCorePortfolioofOperatingPropertiesandExcludesDevelopmentRedevelopmentandHeldforSaleDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesLineItems_97849d0f-c4de-48d3-af3a-f49bb143e864" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstatePropertiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfRealEstateProperties_7040eef0-7cf8-4d38-9280-9214ed0ba3ca" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NumberOfRealEstateProperties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_97849d0f-c4de-48d3-af3a-f49bb143e864" xlink:to="loc_us-gaap_NumberOfRealEstateProperties_7040eef0-7cf8-4d38-9280-9214ed0ba3ca" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AreaOfRealEstateProperty_1c239b97-bef6-4c6f-b57d-fdb182563995" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AreaOfRealEstateProperty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_97849d0f-c4de-48d3-af3a-f49bb143e864" xlink:to="loc_us-gaap_AreaOfRealEstateProperty_1c239b97-bef6-4c6f-b57d-fdb182563995" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_80e89ea9-2590-4597-a4ed-3726afff5eb8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfRealEstatePropertiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_97849d0f-c4de-48d3-af3a-f49bb143e864" xlink:to="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_80e89ea9-2590-4597-a4ed-3726afff5eb8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_d46f05d0-e950-4852-a3cb-87272272c521" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_80e89ea9-2590-4597-a4ed-3726afff5eb8" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_d46f05d0-e950-4852-a3cb-87272272c521" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_d46f05d0-e950-4852-a3cb-87272272c521_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_d46f05d0-e950-4852-a3cb-87272272c521" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_d46f05d0-e950-4852-a3cb-87272272c521_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_9504e034-0bcf-4674-bef4-9c7b970fde4a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_d46f05d0-e950-4852-a3cb-87272272c521" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_9504e034-0bcf-4674-bef4-9c7b970fde4a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_CorePropertiesMember_947ea7fa-3cc6-4ab6-a276-59db8eb3d395" xlink:href="bdn-20230630.xsd#bdn_CorePropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_9504e034-0bcf-4674-bef4-9c7b970fde4a" xlink:to="loc_bdn_CorePropertiesMember_947ea7fa-3cc6-4ab6-a276-59db8eb3d395" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_OfficePropertiesMember_693f12b7-6794-425c-a756-e98ea9bf6b1f" xlink:href="bdn-20230630.xsd#bdn_OfficePropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_CorePropertiesMember_947ea7fa-3cc6-4ab6-a276-59db8eb3d395" xlink:to="loc_bdn_OfficePropertiesMember_693f12b7-6794-425c-a756-e98ea9bf6b1f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_MixedUsePropertiesMember_5998fbcd-8462-4b57-89f9-f9442138e88f" xlink:href="bdn-20230630.xsd#bdn_MixedUsePropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_CorePropertiesMember_947ea7fa-3cc6-4ab6-a276-59db8eb3d395" xlink:to="loc_bdn_MixedUsePropertiesMember_5998fbcd-8462-4b57-89f9-f9442138e88f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_DevelopmentProjectsMember_fa120c30-55ee-4b64-ba98-a3b2a444d355" xlink:href="bdn-20230630.xsd#bdn_DevelopmentProjectsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_9504e034-0bcf-4674-bef4-9c7b970fde4a" xlink:to="loc_bdn_DevelopmentProjectsMember_fa120c30-55ee-4b64-ba98-a3b2a444d355" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_RedevelopmentProjectsMember_6dbf1497-ab2e-41d9-8bd7-b79afe3f2cff" xlink:href="bdn-20230630.xsd#bdn_RedevelopmentProjectsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_9504e034-0bcf-4674-bef4-9c7b970fde4a" xlink:to="loc_bdn_RedevelopmentProjectsMember_6dbf1497-ab2e-41d9-8bd7-b79afe3f2cff" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/REALESTATEINVESTMENTSScheduleofGrossCarryingValueofOperatingPropertiesDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#REALESTATEINVESTMENTSScheduleofGrossCarryingValueofOperatingPropertiesDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/REALESTATEINVESTMENTSScheduleofGrossCarryingValueofOperatingPropertiesDetails" xlink:type="extended" id="i253fcdfd79f649afa1159b4f6383a1ac_REALESTATEINVESTMENTSScheduleofGrossCarryingValueofOperatingPropertiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_1727c2d0-edd1-48b7-89f5-8c4251971ad8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongLivedAssetsHeldForSaleLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Land_d2d4dbeb-d93c-4ed7-9eeb-b336a089998a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Land"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_1727c2d0-edd1-48b7-89f5-8c4251971ad8" xlink:to="loc_us-gaap_Land_d2d4dbeb-d93c-4ed7-9eeb-b336a089998a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentBuildingAndBuildingImprovements_fb2921a0-142b-410a-b82b-57ec6aed6bc2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentBuildingAndBuildingImprovements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_1727c2d0-edd1-48b7-89f5-8c4251971ad8" xlink:to="loc_us-gaap_InvestmentBuildingAndBuildingImprovements_fb2921a0-142b-410a-b82b-57ec6aed6bc2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TenantImprovements_0ffaac26-6087-4c79-acde-2a3e25ed378c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TenantImprovements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_1727c2d0-edd1-48b7-89f5-8c4251971ad8" xlink:to="loc_us-gaap_TenantImprovements_0ffaac26-6087-4c79-acde-2a3e25ed378c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_RealEstateInvestmentPropertyHeldForUseAndSale_2e05d683-85b9-4238-a307-143e6d2bc20d" xlink:href="bdn-20230630.xsd#bdn_RealEstateInvestmentPropertyHeldForUseAndSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_1727c2d0-edd1-48b7-89f5-8c4251971ad8" xlink:to="loc_bdn_RealEstateInvestmentPropertyHeldForUseAndSale_2e05d683-85b9-4238-a307-143e6d2bc20d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_75dd5969-514f-4370-875e-73374c1e7a1b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_1727c2d0-edd1-48b7-89f5-8c4251971ad8" xlink:to="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_75dd5969-514f-4370-875e-73374c1e7a1b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOperatingActivitiesSegmentAxis_cf9fa660-33ba-4376-a387-fe27e563257d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOperatingActivitiesSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_75dd5969-514f-4370-875e-73374c1e7a1b" xlink:to="loc_us-gaap_StatementOperatingActivitiesSegmentAxis_cf9fa660-33ba-4376-a387-fe27e563257d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentOperatingActivitiesDomain_cf9fa660-33ba-4376-a387-fe27e563257d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentOperatingActivitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementOperatingActivitiesSegmentAxis_cf9fa660-33ba-4376-a387-fe27e563257d" xlink:to="loc_us-gaap_SegmentOperatingActivitiesDomain_cf9fa660-33ba-4376-a387-fe27e563257d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentOperatingActivitiesDomain_3ad1cb9d-ef20-4d21-b16a-1216b5006a8b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentOperatingActivitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementOperatingActivitiesSegmentAxis_cf9fa660-33ba-4376-a387-fe27e563257d" xlink:to="loc_us-gaap_SegmentOperatingActivitiesDomain_3ad1cb9d-ef20-4d21-b16a-1216b5006a8b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDiscontinuedOperationsMember_7eac606e-ac68-4814-bc33-654621d390ba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentOperatingActivitiesDomain_3ad1cb9d-ef20-4d21-b16a-1216b5006a8b" xlink:to="loc_us-gaap_SegmentDiscontinuedOperationsMember_7eac606e-ac68-4814-bc33-654621d390ba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentContinuingOperationsMember_4c8d6ddb-b11a-419c-9411-4ac76e425189" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentContinuingOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentOperatingActivitiesDomain_3ad1cb9d-ef20-4d21-b16a-1216b5006a8b" xlink:to="loc_us-gaap_SegmentContinuingOperationsMember_4c8d6ddb-b11a-419c-9411-4ac76e425189" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/REALESTATEINVESTMENTSNarrativeDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#REALESTATEINVESTMENTSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/REALESTATEINVESTMENTSNarrativeDetails" xlink:type="extended" id="iacf46088f7ed4f4bb3bc91a3fbb6962c_REALESTATEINVESTMENTSNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesLineItems_91ba9e76-ac05-4008-89ef-1f603677cf7e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstatePropertiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_OperatingLeaseCostsCapitalized_e08c2eed-5673-4708-8c0a-e49a29bec8bf" xlink:href="bdn-20230630.xsd#bdn_OperatingLeaseCostsCapitalized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_91ba9e76-ac05-4008-89ef-1f603677cf7e" xlink:to="loc_bdn_OperatingLeaseCostsCapitalized_e08c2eed-5673-4708-8c0a-e49a29bec8bf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetRentableArea_12e68d90-cca5-4de4-9ae8-7441c520b6b6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetRentableArea"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_91ba9e76-ac05-4008-89ef-1f603677cf7e" xlink:to="loc_us-gaap_NetRentableArea_12e68d90-cca5-4de4-9ae8-7441c520b6b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnSalesOfInvestmentRealEstate_85e47a87-887d-4582-bd08-1d4a75df09f1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainsLossesOnSalesOfInvestmentRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_91ba9e76-ac05-4008-89ef-1f603677cf7e" xlink:to="loc_us-gaap_GainsLossesOnSalesOfInvestmentRealEstate_85e47a87-887d-4582-bd08-1d4a75df09f1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_9c0dcda1-0159-4b94-9a01-d277813d0ee4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_91ba9e76-ac05-4008-89ef-1f603677cf7e" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_9c0dcda1-0159-4b94-9a01-d277813d0ee4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf_37115e30-066a-486c-be2e-1c0ca0544da9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_91ba9e76-ac05-4008-89ef-1f603677cf7e" xlink:to="loc_us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf_37115e30-066a-486c-be2e-1c0ca0544da9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_0e9010a3-5555-4d0f-ab95-bc8a962643a6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfRealEstatePropertiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_91ba9e76-ac05-4008-89ef-1f603677cf7e" xlink:to="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_0e9010a3-5555-4d0f-ab95-bc8a962643a6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_4db13696-1426-4001-bc89-25a7177de88b" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_0e9010a3-5555-4d0f-ab95-bc8a962643a6" xlink:to="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_4db13696-1426-4001-bc89-25a7177de88b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_4db13696-1426-4001-bc89-25a7177de88b_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_4db13696-1426-4001-bc89-25a7177de88b" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_4db13696-1426-4001-bc89-25a7177de88b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_1b6c6757-fd29-49e9-96be-dad9012678b9" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_4db13696-1426-4001-bc89-25a7177de88b" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_1b6c6757-fd29-49e9-96be-dad9012678b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdsAndLeaseholdImprovementsMember_bd58b3e3-7790-4100-8dd0-4382f38fff71" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LeaseholdsAndLeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_1b6c6757-fd29-49e9-96be-dad9012678b9" xlink:to="loc_us-gaap_LeaseholdsAndLeaseholdImprovementsMember_bd58b3e3-7790-4100-8dd0-4382f38fff71" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_86ab08b3-d5b5-48f6-bd42-37b40f9779ac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_0e9010a3-5555-4d0f-ab95-bc8a962643a6" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_86ab08b3-d5b5-48f6-bd42-37b40f9779ac" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_86ab08b3-d5b5-48f6-bd42-37b40f9779ac_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_86ab08b3-d5b5-48f6-bd42-37b40f9779ac" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_86ab08b3-d5b5-48f6-bd42-37b40f9779ac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_9d725811-bffa-4eb7-97bf-92dc05197884" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_86ab08b3-d5b5-48f6-bd42-37b40f9779ac" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_9d725811-bffa-4eb7-97bf-92dc05197884" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_A3151MarketStreetMember_5eee134d-9073-402d-bf27-2211ddb8bb0a" xlink:href="bdn-20230630.xsd#bdn_A3151MarketStreetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_9d725811-bffa-4eb7-97bf-92dc05197884" xlink:to="loc_bdn_A3151MarketStreetMember_5eee134d-9073-402d-bf27-2211ddb8bb0a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_881d8fb2-9ecb-400d-9ac7-03b5362945e0" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_0e9010a3-5555-4d0f-ab95-bc8a962643a6" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_881d8fb2-9ecb-400d-9ac7-03b5362945e0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_881d8fb2-9ecb-400d-9ac7-03b5362945e0_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_881d8fb2-9ecb-400d-9ac7-03b5362945e0" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_881d8fb2-9ecb-400d-9ac7-03b5362945e0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_8e7155cc-a7e7-4b9e-afe1-623439cf9c9c" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_881d8fb2-9ecb-400d-9ac7-03b5362945e0" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_8e7155cc-a7e7-4b9e-afe1-623439cf9c9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_AustinTexasMember_93d93021-a670-48a4-90eb-feddf863beb2" xlink:href="bdn-20230630.xsd#bdn_AustinTexasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_8e7155cc-a7e7-4b9e-afe1-623439cf9c9c" xlink:to="loc_bdn_AustinTexasMember_93d93021-a670-48a4-90eb-feddf863beb2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_182ab01e-b99b-4aa4-9be8-51a6b4a2e22c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_0e9010a3-5555-4d0f-ab95-bc8a962643a6" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_182ab01e-b99b-4aa4-9be8-51a6b4a2e22c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_182ab01e-b99b-4aa4-9be8-51a6b4a2e22c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_182ab01e-b99b-4aa4-9be8-51a6b4a2e22c" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_182ab01e-b99b-4aa4-9be8-51a6b4a2e22c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_785283f2-c3bc-4869-aab9-300d6dbf0dce" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_182ab01e-b99b-4aa4-9be8-51a6b4a2e22c" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_785283f2-c3bc-4869-aab9-300d6dbf0dce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_5deced54-c594-4623-8567-f214dcd65b71" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_785283f2-c3bc-4869-aab9-300d6dbf0dce" xlink:to="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_5deced54-c594-4623-8567-f214dcd65b71" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/REALESTATEINVESTMENTSScheduleofPropertiesClassifiedasHeldforSaleDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#REALESTATEINVESTMENTSScheduleofPropertiesClassifiedasHeldforSaleDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/REALESTATEINVESTMENTSScheduleofPropertiesClassifiedasHeldforSaleDetails" xlink:type="extended" id="if88d29cd1fbd47edbe806045767c9213_REALESTATEINVESTMENTSScheduleofPropertiesClassifiedasHeldforSaleDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_f273ad40-6cb8-4dcf-a0aa-e425c89661e1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongLivedAssetsHeldForSaleLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_aa7f2ad4-607e-4b8b-b728-06ad7b4c11ac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_f273ad40-6cb8-4dcf-a0aa-e425c89661e1" xlink:to="loc_us-gaap_AssetsAbstract_aa7f2ad4-607e-4b8b-b728-06ad7b4c11ac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentsAbstract_564d1082-f748-45aa-98b5-153f36653f46" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateInvestmentsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_aa7f2ad4-607e-4b8b-b728-06ad7b4c11ac" xlink:to="loc_us-gaap_RealEstateInvestmentsAbstract_564d1082-f748-45aa-98b5-153f36653f46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateHeldforsale_9203656c-8bcd-4332-865d-1a5869d44392" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateHeldforsale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstateInvestmentsAbstract_564d1082-f748-45aa-98b5-153f36653f46" xlink:to="loc_us-gaap_RealEstateHeldforsale_9203656c-8bcd-4332-865d-1a5869d44392" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation_5b428d89-c0e6-45b7-b645-9888f280843a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstateInvestmentsAbstract_564d1082-f748-45aa-98b5-153f36653f46" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation_5b428d89-c0e6-45b7-b645-9888f280843a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyAtCost_07bdde55-5aaf-4bdd-a927-c5fdf8a881a4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateInvestmentPropertyAtCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstateInvestmentsAbstract_564d1082-f748-45aa-98b5-153f36653f46" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyAtCost_07bdde55-5aaf-4bdd-a927-c5fdf8a881a4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyNet_c9d80eeb-830d-452e-aa65-7f23b213304f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateInvestmentPropertyNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstateInvestmentsAbstract_564d1082-f748-45aa-98b5-153f36653f46" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyNet_c9d80eeb-830d-452e-aa65-7f23b213304f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCostsCurrentAndNoncurrent_f27def4e-f5f4-460f-8312-2af506aab779" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredCostsCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_aa7f2ad4-607e-4b8b-b728-06ad7b4c11ac" xlink:to="loc_us-gaap_DeferredCostsCurrentAndNoncurrent_f27def4e-f5f4-460f-8312-2af506aab779" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_39d9e58d-4a78-464e-9e2e-f97ee46e97cb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_aa7f2ad4-607e-4b8b-b728-06ad7b4c11ac" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_39d9e58d-4a78-464e-9e2e-f97ee46e97cb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedInvestmentIncomeReceivable_df3a51f7-e75a-4f14-9ae3-64b109a7cb60" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccruedInvestmentIncomeReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_aa7f2ad4-607e-4b8b-b728-06ad7b4c11ac" xlink:to="loc_us-gaap_AccruedInvestmentIncomeReceivable_df3a51f7-e75a-4f14-9ae3-64b109a7cb60" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_3a588ad2-df76-438a-a060-5eb20c4d82c4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_aa7f2ad4-607e-4b8b-b728-06ad7b4c11ac" xlink:to="loc_us-gaap_OtherAssets_3a588ad2-df76-438a-a060-5eb20c4d82c4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_a3d68dc6-f817-4774-b0a9-696161f1a6cf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_aa7f2ad4-607e-4b8b-b728-06ad7b4c11ac" xlink:to="loc_us-gaap_Assets_a3d68dc6-f817-4774-b0a9-696161f1a6cf" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAbstract_adde65e6-b5e5-40ab-8de4-0dcbf7f70a8c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_f273ad40-6cb8-4dcf-a0aa-e425c89661e1" xlink:to="loc_us-gaap_LiabilitiesAbstract_adde65e6-b5e5-40ab-8de4-0dcbf7f70a8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebt_c66ddb27-316d-449c-94d1-d941e0eab15a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_adde65e6-b5e5-40ab-8de4-0dcbf7f70a8c" xlink:to="loc_us-gaap_SecuredDebt_c66ddb27-316d-449c-94d1-d941e0eab15a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_fbac1933-31a4-43fe-90f4-a314acf13039" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_adde65e6-b5e5-40ab-8de4-0dcbf7f70a8c" xlink:to="loc_us-gaap_ContractWithCustomerLiability_fbac1933-31a4-43fe-90f4-a314acf13039" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BelowMarketLeaseNet_df90f2b7-212e-44d7-8de7-befe4899effe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BelowMarketLeaseNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_adde65e6-b5e5-40ab-8de4-0dcbf7f70a8c" xlink:to="loc_us-gaap_BelowMarketLeaseNet_df90f2b7-212e-44d7-8de7-befe4899effe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_be9ee0ae-f323-4298-9f3e-1d8441b058b9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_adde65e6-b5e5-40ab-8de4-0dcbf7f70a8c" xlink:to="loc_us-gaap_Liabilities_be9ee0ae-f323-4298-9f3e-1d8441b058b9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_9c3ee102-95e6-4655-82f7-be634bae28f4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_f273ad40-6cb8-4dcf-a0aa-e425c89661e1" xlink:to="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_9c3ee102-95e6-4655-82f7-be634bae28f4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_fbc7b792-531c-4954-9587-076273a94bab" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_9c3ee102-95e6-4655-82f7-be634bae28f4" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_fbc7b792-531c-4954-9587-076273a94bab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_fbc7b792-531c-4954-9587-076273a94bab_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_fbc7b792-531c-4954-9587-076273a94bab" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_fbc7b792-531c-4954-9587-076273a94bab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_255abd88-05b9-40ca-87b4-bbe132e7374d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_fbc7b792-531c-4954-9587-076273a94bab" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_255abd88-05b9-40ca-87b4-bbe132e7374d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_bc64b306-519c-4321-be95-7a50cb4527ce" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_255abd88-05b9-40ca-87b4-bbe132e7374d" xlink:to="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_bc64b306-519c-4321-be95-7a50cb4527ce" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_ab8f1347-1d15-4359-9615-27154b02e06a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_9c3ee102-95e6-4655-82f7-be634bae28f4" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_ab8f1347-1d15-4359-9615-27154b02e06a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_ab8f1347-1d15-4359-9615-27154b02e06a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_ab8f1347-1d15-4359-9615-27154b02e06a" xlink:to="loc_us-gaap_SegmentDomain_ab8f1347-1d15-4359-9615-27154b02e06a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_9e5fb1ec-bfaa-421b-9bcc-c0581434123d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_ab8f1347-1d15-4359-9615-27154b02e06a" xlink:to="loc_us-gaap_SegmentDomain_9e5fb1ec-bfaa-421b-9bcc-c0581434123d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_PennsylvaniaSuburbsSegmentMember_590449a1-2a2f-4bc8-9e15-c6da9182d237" xlink:href="bdn-20230630.xsd#bdn_PennsylvaniaSuburbsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_9e5fb1ec-bfaa-421b-9bcc-c0581434123d" xlink:to="loc_bdn_PennsylvaniaSuburbsSegmentMember_590449a1-2a2f-4bc8-9e15-c6da9182d237" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_58d2e17c-ee27-4bb4-b72b-dddb2b10021f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_9c3ee102-95e6-4655-82f7-be634bae28f4" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_58d2e17c-ee27-4bb4-b72b-dddb2b10021f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_58d2e17c-ee27-4bb4-b72b-dddb2b10021f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_58d2e17c-ee27-4bb4-b72b-dddb2b10021f" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_58d2e17c-ee27-4bb4-b72b-dddb2b10021f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ee8c1e74-4199-4d89-940b-a3b6e410ef42" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_58d2e17c-ee27-4bb4-b72b-dddb2b10021f" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ee8c1e74-4199-4d89-940b-a3b6e410ef42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_RealEstateExcludingConstructionInProgressMember_37049b72-4f68-4fde-ad6c-fda258b6ec6c" xlink:href="bdn-20230630.xsd#bdn_RealEstateExcludingConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ee8c1e74-4199-4d89-940b-a3b6e410ef42" xlink:to="loc_bdn_RealEstateExcludingConstructionInProgressMember_37049b72-4f68-4fde-ad6c-fda258b6ec6c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_e327e207-499c-41c9-bc8c-fa3ffab34def" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ee8c1e74-4199-4d89-940b-a3b6e410ef42" xlink:to="loc_us-gaap_ConstructionInProgressMember_e327e207-499c-41c9-bc8c-fa3ffab34def" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESNarrativeDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESNarrativeDetails" xlink:type="extended" id="ic4d2258bfd6d47b48674029a21fd1388_INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5cd07d02-e07f-4c25-b3f9-e7c392cb70f3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfRealEstateProperties_b270b867-6774-4147-8444-4d3dd7cebc31" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NumberOfRealEstateProperties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5cd07d02-e07f-4c25-b3f9-e7c392cb70f3" xlink:to="loc_us-gaap_NumberOfRealEstateProperties_b270b867-6774-4147-8444-4d3dd7cebc31" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_7c0524cc-9c09-4e7a-906f-99992632ca1d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5cd07d02-e07f-4c25-b3f9-e7c392cb70f3" xlink:to="loc_us-gaap_EquityMethodInvestments_7c0524cc-9c09-4e7a-906f-99992632ca1d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_NumberOfRealEstatePropertiesWithNegativeInvestmentBalances_cd90c885-641e-4ad8-a4e6-bbe20c43ec6f" xlink:href="bdn-20230630.xsd#bdn_NumberOfRealEstatePropertiesWithNegativeInvestmentBalances"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5cd07d02-e07f-4c25-b3f9-e7c392cb70f3" xlink:to="loc_bdn_NumberOfRealEstatePropertiesWithNegativeInvestmentBalances_cd90c885-641e-4ad8-a4e6-bbe20c43ec6f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_NumberOfUnconsolidatedInvestmentsInRealEstateVentures_a5eee14b-1b26-42ed-87fe-64041d5d195d" xlink:href="bdn-20230630.xsd#bdn_NumberOfUnconsolidatedInvestmentsInRealEstateVentures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5cd07d02-e07f-4c25-b3f9-e7c392cb70f3" xlink:to="loc_bdn_NumberOfUnconsolidatedInvestmentsInRealEstateVentures_a5eee14b-1b26-42ed-87fe-64041d5d195d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetRentableArea_819894a1-0f4e-4edd-9f0e-e9a8ac9c59fe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetRentableArea"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5cd07d02-e07f-4c25-b3f9-e7c392cb70f3" xlink:to="loc_us-gaap_NetRentableArea_819894a1-0f4e-4edd-9f0e-e9a8ac9c59fe" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AreaOfLand_8891c593-ddcf-4c71-a76c-cfe32170eb36" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AreaOfLand"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5cd07d02-e07f-4c25-b3f9-e7c392cb70f3" xlink:to="loc_us-gaap_AreaOfLand_8891c593-ddcf-4c71-a76c-cfe32170eb36" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfUnitsInRealEstateProperty_05810bcc-70a3-4cd1-9049-60f5ed1cd1a5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NumberOfUnitsInRealEstateProperty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5cd07d02-e07f-4c25-b3f9-e7c392cb70f3" xlink:to="loc_us-gaap_NumberOfUnitsInRealEstateProperty_05810bcc-70a3-4cd1-9049-60f5ed1cd1a5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_03ab4948-5f33-421b-9722-e59434d019e3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5cd07d02-e07f-4c25-b3f9-e7c392cb70f3" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_03ab4948-5f33-421b-9722-e59434d019e3" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_97d72be0-66c0-4d0b-be77-9ffbde08e932" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5cd07d02-e07f-4c25-b3f9-e7c392cb70f3" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_97d72be0-66c0-4d0b-be77-9ffbde08e932" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNet_a18c73ab-7232-4916-8874-15593fddc433" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5cd07d02-e07f-4c25-b3f9-e7c392cb70f3" xlink:to="loc_us-gaap_AccountsReceivableNet_a18c73ab-7232-4916-8874-15593fddc433" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_0430137e-41b9-4a72-b96b-25d0a35361c6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5cd07d02-e07f-4c25-b3f9-e7c392cb70f3" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_0430137e-41b9-4a72-b96b-25d0a35361c6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_b38b0d92-3d8d-419a-a9ac-9da2ba09ca6e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_0430137e-41b9-4a72-b96b-25d0a35361c6" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_b38b0d92-3d8d-419a-a9ac-9da2ba09ca6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_b38b0d92-3d8d-419a-a9ac-9da2ba09ca6e_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_b38b0d92-3d8d-419a-a9ac-9da2ba09ca6e" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_b38b0d92-3d8d-419a-a9ac-9da2ba09ca6e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_64d3c54a-c079-4e26-86a7-7fc1f3a54466" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_b38b0d92-3d8d-419a-a9ac-9da2ba09ca6e" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_64d3c54a-c079-4e26-86a7-7fc1f3a54466" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_UnconsolidatedRealEstateVenturesMember_c1206fce-2209-4b15-9a37-5db464f4f3f8" xlink:href="bdn-20230630.xsd#bdn_UnconsolidatedRealEstateVenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_64d3c54a-c079-4e26-86a7-7fc1f3a54466" xlink:to="loc_bdn_UnconsolidatedRealEstateVenturesMember_c1206fce-2209-4b15-9a37-5db464f4f3f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_1ac31484-404e-4892-8f67-b79173c48458" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_0430137e-41b9-4a72-b96b-25d0a35361c6" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_1ac31484-404e-4892-8f67-b79173c48458" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1ac31484-404e-4892-8f67-b79173c48458_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_1ac31484-404e-4892-8f67-b79173c48458" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1ac31484-404e-4892-8f67-b79173c48458_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_46869a93-2512-450b-b0e5-ad8bccd9a4b5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_1ac31484-404e-4892-8f67-b79173c48458" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_46869a93-2512-450b-b0e5-ad8bccd9a4b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnconsolidatedPropertiesMember_dc967c1a-047d-4245-8441-fa954cfb6bdb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnconsolidatedPropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_46869a93-2512-450b-b0e5-ad8bccd9a4b5" xlink:to="loc_us-gaap_UnconsolidatedPropertiesMember_dc967c1a-047d-4245-8441-fa954cfb6bdb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_LandHeldForDevelopmentMember_6844c0e8-3d8e-4d70-990a-33fb2f81166c" xlink:href="bdn-20230630.xsd#bdn_LandHeldForDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_46869a93-2512-450b-b0e5-ad8bccd9a4b5" xlink:to="loc_bdn_LandHeldForDevelopmentMember_6844c0e8-3d8e-4d70-990a-33fb2f81166c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_LandUnderActiveDevelopmentMember_ac56be49-a5ba-45c8-bd3d-f89d4e497d1e" xlink:href="bdn-20230630.xsd#bdn_LandUnderActiveDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_46869a93-2512-450b-b0e5-ad8bccd9a4b5" xlink:to="loc_bdn_LandUnderActiveDevelopmentMember_ac56be49-a5ba-45c8-bd3d-f89d4e497d1e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_MixedUseTowerMember_bfc20242-f661-4115-bca3-d3a1dfa637a0" xlink:href="bdn-20230630.xsd#bdn_MixedUseTowerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_46869a93-2512-450b-b0e5-ad8bccd9a4b5" xlink:to="loc_bdn_MixedUseTowerMember_bfc20242-f661-4115-bca3-d3a1dfa637a0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_c6956e68-0af9-4399-9187-26fbc3ab8e24" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_0430137e-41b9-4a72-b96b-25d0a35361c6" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_c6956e68-0af9-4399-9187-26fbc3ab8e24" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_c6956e68-0af9-4399-9187-26fbc3ab8e24_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_c6956e68-0af9-4399-9187-26fbc3ab8e24" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_c6956e68-0af9-4399-9187-26fbc3ab8e24_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_379a4695-3b11-4d89-b929-97a38b80bcc0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_c6956e68-0af9-4399-9187-26fbc3ab8e24" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_379a4695-3b11-4d89-b929-97a38b80bcc0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesMember_a9a56257-c9f0-456a-8693-7dd770b412e7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_379a4695-3b11-4d89-b929-97a38b80bcc0" xlink:to="loc_us-gaap_OtherLiabilitiesMember_a9a56257-c9f0-456a-8693-7dd770b412e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_39f9ae77-35ef-4f54-b408-df847819df2c" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_0430137e-41b9-4a72-b96b-25d0a35361c6" xlink:to="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_39f9ae77-35ef-4f54-b408-df847819df2c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_39f9ae77-35ef-4f54-b408-df847819df2c_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_39f9ae77-35ef-4f54-b408-df847819df2c" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_39f9ae77-35ef-4f54-b408-df847819df2c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_957f30c2-7484-4106-a9a0-0e88c2120998" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_39f9ae77-35ef-4f54-b408-df847819df2c" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_957f30c2-7484-4106-a9a0-0e88c2120998" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OfficeBuildingMember_3b0b1efa-90ec-4728-afa2-349476d5de26" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_OfficeBuildingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_957f30c2-7484-4106-a9a0-0e88c2120998" xlink:to="loc_srt_OfficeBuildingMember_3b0b1efa-90ec-4728-afa2-349476d5de26" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_b55cb6ec-12f2-403f-927e-82df7e3af2c4" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_0430137e-41b9-4a72-b96b-25d0a35361c6" xlink:to="loc_srt_RangeAxis_b55cb6ec-12f2-403f-927e-82df7e3af2c4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_b55cb6ec-12f2-403f-927e-82df7e3af2c4_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_b55cb6ec-12f2-403f-927e-82df7e3af2c4" xlink:to="loc_srt_RangeMember_b55cb6ec-12f2-403f-927e-82df7e3af2c4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_7869267d-577a-4339-a8b2-b2178c5f3032" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_b55cb6ec-12f2-403f-927e-82df7e3af2c4" xlink:to="loc_srt_RangeMember_7869267d-577a-4339-a8b2-b2178c5f3032" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_5dd2fb84-970f-493e-bbf6-0bededf5b51e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_7869267d-577a-4339-a8b2-b2178c5f3032" xlink:to="loc_srt_MinimumMember_5dd2fb84-970f-493e-bbf6-0bededf5b51e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_41605da5-a61f-4d80-99d7-c4a4f3ea2143" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_7869267d-577a-4339-a8b2-b2178c5f3032" xlink:to="loc_srt_MaximumMember_41605da5-a61f-4d80-99d7-c4a4f3ea2143" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_9e3004b6-4b9d-4ff1-abef-6bc52406af93" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_0430137e-41b9-4a72-b96b-25d0a35361c6" xlink:to="loc_srt_ProductOrServiceAxis_9e3004b6-4b9d-4ff1-abef-6bc52406af93" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_9e3004b6-4b9d-4ff1-abef-6bc52406af93_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_9e3004b6-4b9d-4ff1-abef-6bc52406af93" xlink:to="loc_srt_ProductsAndServicesDomain_9e3004b6-4b9d-4ff1-abef-6bc52406af93_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_d8a76d1e-e37c-46dc-8413-83bd569a4fdf" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_9e3004b6-4b9d-4ff1-abef-6bc52406af93" xlink:to="loc_srt_ProductsAndServicesDomain_d8a76d1e-e37c-46dc-8413-83bd569a4fdf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_ManagementFeesMember_83add22c-0458-46d9-89bc-86c8747f2fd9" xlink:href="bdn-20230630.xsd#bdn_ManagementFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d8a76d1e-e37c-46dc-8413-83bd569a4fdf" xlink:to="loc_bdn_ManagementFeesMember_83add22c-0458-46d9-89bc-86c8747f2fd9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_LeaseCommissionIncomeMember_a55f49a6-da46-471c-9470-b2cf2fe01e62" xlink:href="bdn-20230630.xsd#bdn_LeaseCommissionIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d8a76d1e-e37c-46dc-8413-83bd569a4fdf" xlink:to="loc_bdn_LeaseCommissionIncomeMember_a55f49a6-da46-471c-9470-b2cf2fe01e62" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_InvestmentsSecondaryCategorizationAxis_ec9064e8-c448-4764-b2bb-44fb4443fa09" xlink:href="bdn-20230630.xsd#bdn_InvestmentsSecondaryCategorizationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_0430137e-41b9-4a72-b96b-25d0a35361c6" xlink:to="loc_bdn_InvestmentsSecondaryCategorizationAxis_ec9064e8-c448-4764-b2bb-44fb4443fa09" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_InvestmentsSecondaryCategorizationDomain_ec9064e8-c448-4764-b2bb-44fb4443fa09_default" xlink:href="bdn-20230630.xsd#bdn_InvestmentsSecondaryCategorizationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_bdn_InvestmentsSecondaryCategorizationAxis_ec9064e8-c448-4764-b2bb-44fb4443fa09" xlink:to="loc_bdn_InvestmentsSecondaryCategorizationDomain_ec9064e8-c448-4764-b2bb-44fb4443fa09_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_InvestmentsSecondaryCategorizationDomain_04639377-265d-459e-a5c3-81f7b9e4fa8a" xlink:href="bdn-20230630.xsd#bdn_InvestmentsSecondaryCategorizationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_bdn_InvestmentsSecondaryCategorizationAxis_ec9064e8-c448-4764-b2bb-44fb4443fa09" xlink:to="loc_bdn_InvestmentsSecondaryCategorizationDomain_04639377-265d-459e-a5c3-81f7b9e4fa8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_RealEstateVentureMember_6e5a5f55-4196-4b86-b50e-7e4df50fdc06" xlink:href="bdn-20230630.xsd#bdn_RealEstateVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_InvestmentsSecondaryCategorizationDomain_04639377-265d-459e-a5c3-81f7b9e4fa8a" xlink:to="loc_bdn_RealEstateVentureMember_6e5a5f55-4196-4b86-b50e-7e4df50fdc06" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESSummaryofFinancialPositionofRealEstateVenturesDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESSummaryofFinancialPositionofRealEstateVenturesDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESSummaryofFinancialPositionofRealEstateVenturesDetails" xlink:type="extended" id="id405a09fe38948b1a8a4b9bfa997b67f_INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESSummaryofFinancialPositionofRealEstateVenturesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_f3286c39-37d0-4d57-9201-055ea970b605" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyNet_861ac80b-9f0b-4ecb-a556-346c25a1eb21" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateInvestmentPropertyNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_f3286c39-37d0-4d57-9201-055ea970b605" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyNet_861ac80b-9f0b-4ecb-a556-346c25a1eb21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_d1076415-df67-4839-b27d-27edd0768e99" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_f3286c39-37d0-4d57-9201-055ea970b605" xlink:to="loc_us-gaap_OtherAssets_d1076415-df67-4839-b27d-27edd0768e99" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities_6461bf20-29d1-4bad-a2c3-9769ec4bf4fd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_f3286c39-37d0-4d57-9201-055ea970b605" xlink:to="loc_us-gaap_OtherLiabilities_6461bf20-29d1-4bad-a2c3-9769ec4bf4fd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_7c281491-1520-43d7-9611-716fd5e5cd4b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_f3286c39-37d0-4d57-9201-055ea970b605" xlink:to="loc_us-gaap_LongTermDebt_7c281491-1520-43d7-9611-716fd5e5cd4b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_0549c644-9ccd-497d-b47b-879c240b5f58" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_f3286c39-37d0-4d57-9201-055ea970b605" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_0549c644-9ccd-497d-b47b-879c240b5f58" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_8a89a261-58f7-465f-9b6c-2c8ffbac171a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_f3286c39-37d0-4d57-9201-055ea970b605" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_8a89a261-58f7-465f-9b6c-2c8ffbac171a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_1be04505-2719-4ef4-8374-931042ff5625" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_8a89a261-58f7-465f-9b6c-2c8ffbac171a" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_1be04505-2719-4ef4-8374-931042ff5625" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_1be04505-2719-4ef4-8374-931042ff5625_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_1be04505-2719-4ef4-8374-931042ff5625" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_1be04505-2719-4ef4-8374-931042ff5625_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_e850403e-5eb5-400d-95ce-d9f00818e84c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_1be04505-2719-4ef4-8374-931042ff5625" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_e850403e-5eb5-400d-95ce-d9f00818e84c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember_bd8652c9-7ae3-4daf-bb05-6345b9b372b0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_e850403e-5eb5-400d-95ce-d9f00818e84c" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember_bd8652c9-7ae3-4daf-bb05-6345b9b372b0" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESSummaryofResultsofOperationsofRealEstateVentureswithInterestsDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESSummaryofResultsofOperationsofRealEstateVentureswithInterestsDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESSummaryofResultsofOperationsofRealEstateVentureswithInterestsDetails" xlink:type="extended" id="i7a8298bdd84e41b88a332c03d90487a1_INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESSummaryofResultsofOperationsofRealEstateVentureswithInterestsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_dedb64f9-5571-4c77-8390-4bdcb68f3fb4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_a309519d-fa16-41fe-91b6-7810fab0752d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_dedb64f9-5571-4c77-8390-4bdcb68f3fb4" xlink:to="loc_us-gaap_Revenues_a309519d-fa16-41fe-91b6-7810fab0752d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_4a4f641c-f537-46a3-9eea-9c6b15762ff9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_dedb64f9-5571-4c77-8390-4bdcb68f3fb4" xlink:to="loc_us-gaap_CostsAndExpenses_4a4f641c-f537-46a3-9eea-9c6b15762ff9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseOther_7eb6d37c-f3a8-4f7e-84e4-b0f058c8b100" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpenseOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_dedb64f9-5571-4c77-8390-4bdcb68f3fb4" xlink:to="loc_us-gaap_InterestExpenseOther_7eb6d37c-f3a8-4f7e-84e4-b0f058c8b100" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_cfcdce5d-a129-40f9-b525-8d96435440ce" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_dedb64f9-5571-4c77-8390-4bdcb68f3fb4" xlink:to="loc_us-gaap_DepreciationAndAmortization_cfcdce5d-a129-40f9-b525-8d96435440ce" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_76b46524-746f-4430-bbcb-11711b0920fe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_dedb64f9-5571-4c77-8390-4bdcb68f3fb4" xlink:to="loc_us-gaap_ProfitLoss_76b46524-746f-4430-bbcb-11711b0920fe" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_IncomeLossFromEquityMethodInvestmentsBeforeBasisAdjustmentsAndOther_c039bbd4-6bc6-4be8-a83f-af896f8f6eb4" xlink:href="bdn-20230630.xsd#bdn_IncomeLossFromEquityMethodInvestmentsBeforeBasisAdjustmentsAndOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_dedb64f9-5571-4c77-8390-4bdcb68f3fb4" xlink:to="loc_bdn_IncomeLossFromEquityMethodInvestmentsBeforeBasisAdjustmentsAndOther_c039bbd4-6bc6-4be8-a83f-af896f8f6eb4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_BasisAdjustmentsAndOther_8495d924-94a1-40d0-92f2-dee263c08e15" xlink:href="bdn-20230630.xsd#bdn_BasisAdjustmentsAndOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_dedb64f9-5571-4c77-8390-4bdcb68f3fb4" xlink:to="loc_bdn_BasisAdjustmentsAndOther_8495d924-94a1-40d0-92f2-dee263c08e15" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_0e9c7623-2e27-49cd-8fde-a3bb4948e3c6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_dedb64f9-5571-4c77-8390-4bdcb68f3fb4" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_0e9c7623-2e27-49cd-8fde-a3bb4948e3c6" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_108c4756-0cae-4399-9245-e1c8c94acf58" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_dedb64f9-5571-4c77-8390-4bdcb68f3fb4" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_108c4756-0cae-4399-9245-e1c8c94acf58" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_2db18fd8-3cf0-4bc1-82fb-3c7eefe4cfd4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_108c4756-0cae-4399-9245-e1c8c94acf58" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_2db18fd8-3cf0-4bc1-82fb-3c7eefe4cfd4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_2db18fd8-3cf0-4bc1-82fb-3c7eefe4cfd4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_2db18fd8-3cf0-4bc1-82fb-3c7eefe4cfd4" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_2db18fd8-3cf0-4bc1-82fb-3c7eefe4cfd4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_7c7c1831-522d-4dcf-a60a-8391463735c5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_2db18fd8-3cf0-4bc1-82fb-3c7eefe4cfd4" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_7c7c1831-522d-4dcf-a60a-8391463735c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember_a0f3dcb2-cbd4-44cb-a0b8-311e7c660100" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_7c7c1831-522d-4dcf-a60a-8391463735c5" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember_a0f3dcb2-cbd4-44cb-a0b8-311e7c660100" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESCommerceSquareVentureDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESCommerceSquareVentureDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESCommerceSquareVentureDetails" xlink:type="extended" id="i98599e1ea66448739ead6b1c574c6cfb_INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESCommerceSquareVentureDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_863a6b5c-ae40-42e3-b94e-f9df9eb3be1d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_dceaad12-e4cb-460f-b9de-762fb745d700" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_863a6b5c-ae40-42e3-b94e-f9df9eb3be1d" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_dceaad12-e4cb-460f-b9de-762fb745d700" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_7c50552f-bf05-448f-a4df-b60ffe506379" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_863a6b5c-ae40-42e3-b94e-f9df9eb3be1d" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_7c50552f-bf05-448f-a4df-b60ffe506379" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_23073409-7940-474b-b55f-787aa8bce1a4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsToAcquireEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_863a6b5c-ae40-42e3-b94e-f9df9eb3be1d" xlink:to="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_23073409-7940-474b-b55f-787aa8bce1a4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_784f12a4-20a0-42f3-a850-6011c822c0ed" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_863a6b5c-ae40-42e3-b94e-f9df9eb3be1d" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_784f12a4-20a0-42f3-a850-6011c822c0ed" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_b9b02bba-d923-4c25-aff5-b4e13e864f76" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_863a6b5c-ae40-42e3-b94e-f9df9eb3be1d" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_b9b02bba-d923-4c25-aff5-b4e13e864f76" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_b9a9a615-e1c6-4e1c-b4a4-2639cb746338" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_b9b02bba-d923-4c25-aff5-b4e13e864f76" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_b9a9a615-e1c6-4e1c-b4a4-2639cb746338" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_b9a9a615-e1c6-4e1c-b4a4-2639cb746338_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_b9a9a615-e1c6-4e1c-b4a4-2639cb746338" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_b9a9a615-e1c6-4e1c-b4a4-2639cb746338_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_65f96066-8925-4848-88bd-5317ae3a2c5d" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_b9a9a615-e1c6-4e1c-b4a4-2639cb746338" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_65f96066-8925-4848-88bd-5317ae3a2c5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_CommerceSquareVentureMember_40c0b1a7-2e27-4bf6-8b94-6e1b02df7fff" xlink:href="bdn-20230630.xsd#bdn_CommerceSquareVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_65f96066-8925-4848-88bd-5317ae3a2c5d" xlink:to="loc_bdn_CommerceSquareVentureMember_40c0b1a7-2e27-4bf6-8b94-6e1b02df7fff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_5b0cea44-54a5-4d42-abb3-2cfa057bb9e9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_b9b02bba-d923-4c25-aff5-b4e13e864f76" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_5b0cea44-54a5-4d42-abb3-2cfa057bb9e9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_5b0cea44-54a5-4d42-abb3-2cfa057bb9e9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_5b0cea44-54a5-4d42-abb3-2cfa057bb9e9" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_5b0cea44-54a5-4d42-abb3-2cfa057bb9e9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_afaba620-da2f-4801-835d-501ecba4ec97" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_5b0cea44-54a5-4d42-abb3-2cfa057bb9e9" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_afaba620-da2f-4801-835d-501ecba4ec97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_38a9df32-62b2-49c7-b19c-82f774d1f0e7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_afaba620-da2f-4801-835d-501ecba4ec97" xlink:to="loc_us-gaap_SecuredDebtMember_38a9df32-62b2-49c7-b19c-82f774d1f0e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_01fb802b-0ade-4aa9-8428-f872f598b771" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_b9b02bba-d923-4c25-aff5-b4e13e864f76" xlink:to="loc_us-gaap_InvestmentTypeAxis_01fb802b-0ade-4aa9-8428-f872f598b771" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_01fb802b-0ade-4aa9-8428-f872f598b771_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_01fb802b-0ade-4aa9-8428-f872f598b771" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_01fb802b-0ade-4aa9-8428-f872f598b771_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_5e789bfe-d68b-4cea-99f5-0d7733bd168a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_01fb802b-0ade-4aa9-8428-f872f598b771" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_5e789bfe-d68b-4cea-99f5-0d7733bd168a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_CommonOwnershipInterestSecuritiesMember_5e95b98d-49b9-4438-8e3a-dcdbef850d4b" xlink:href="bdn-20230630.xsd#bdn_CommonOwnershipInterestSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_5e789bfe-d68b-4cea-99f5-0d7733bd168a" xlink:to="loc_bdn_CommonOwnershipInterestSecuritiesMember_5e95b98d-49b9-4438-8e3a-dcdbef850d4b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESMAPVentureDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESMAPVentureDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESMAPVentureDetails" xlink:type="extended" id="i755a923b94774589aae618d1912a08fb_INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESMAPVentureDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_785dd81b-bd0d-4e63-b226-a7078c229a76" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_NumberOfOfficePropertiesOwned_8dcd582d-be8c-4718-b8a5-474901232019" xlink:href="bdn-20230630.xsd#bdn_NumberOfOfficePropertiesOwned"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_785dd81b-bd0d-4e63-b226-a7078c229a76" xlink:to="loc_bdn_NumberOfOfficePropertiesOwned_8dcd582d-be8c-4718-b8a5-474901232019" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetRentableArea_86531867-823f-4322-979a-a4470f132c94" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetRentableArea"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_785dd81b-bd0d-4e63-b226-a7078c229a76" xlink:to="loc_us-gaap_NetRentableArea_86531867-823f-4322-979a-a4470f132c94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfPropertiesSubjectToGroundLeases_507905b9-32fa-4955-a7d6-fb6752310c77" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NumberOfPropertiesSubjectToGroundLeases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_785dd81b-bd0d-4e63-b226-a7078c229a76" xlink:to="loc_us-gaap_NumberOfPropertiesSubjectToGroundLeases_507905b9-32fa-4955-a7d6-fb6752310c77" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsGross_b88215b4-e312-4a16-9b45-64a9bed17bfa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_785dd81b-bd0d-4e63-b226-a7078c229a76" xlink:to="loc_us-gaap_DeferredFinanceCostsGross_b88215b4-e312-4a16-9b45-64a9bed17bfa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentsJointVentures_c9136acc-3943-4b68-bec3-856485f60dde" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateInvestmentsJointVentures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_785dd81b-bd0d-4e63-b226-a7078c229a76" xlink:to="loc_us-gaap_RealEstateInvestmentsJointVentures_c9136acc-3943-4b68-bec3-856485f60dde" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_089e3649-0bd8-4513-ad82-03a9fa3df8e9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_785dd81b-bd0d-4e63-b226-a7078c229a76" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_089e3649-0bd8-4513-ad82-03a9fa3df8e9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_28b85b7b-cd66-413f-a926-9231c37fc52c" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_089e3649-0bd8-4513-ad82-03a9fa3df8e9" xlink:to="loc_srt_ConsolidatedEntitiesAxis_28b85b7b-cd66-413f-a926-9231c37fc52c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_28b85b7b-cd66-413f-a926-9231c37fc52c_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_28b85b7b-cd66-413f-a926-9231c37fc52c" xlink:to="loc_srt_ConsolidatedEntitiesDomain_28b85b7b-cd66-413f-a926-9231c37fc52c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_e0201c52-bdaf-4fe1-8191-94908a263b71" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_28b85b7b-cd66-413f-a926-9231c37fc52c" xlink:to="loc_srt_ConsolidatedEntitiesDomain_e0201c52-bdaf-4fe1-8191-94908a263b71" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember_0b63ce6a-e768-413c-bef1-071ab9b0ee00" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_e0201c52-bdaf-4fe1-8191-94908a263b71" xlink:to="loc_us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember_0b63ce6a-e768-413c-bef1-071ab9b0ee00" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_433cca39-31e8-4fb4-a2db-14d146fb4f6a" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_089e3649-0bd8-4513-ad82-03a9fa3df8e9" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_433cca39-31e8-4fb4-a2db-14d146fb4f6a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_433cca39-31e8-4fb4-a2db-14d146fb4f6a_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_433cca39-31e8-4fb4-a2db-14d146fb4f6a" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_433cca39-31e8-4fb4-a2db-14d146fb4f6a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_91a828bd-9933-4557-89f8-48d9c728ea79" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_433cca39-31e8-4fb4-a2db-14d146fb4f6a" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_91a828bd-9933-4557-89f8-48d9c728ea79" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_MAPVentureMember_bd93a324-ec08-407e-9380-28d29e92ae51" xlink:href="bdn-20230630.xsd#bdn_MAPVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_91a828bd-9933-4557-89f8-48d9c728ea79" xlink:to="loc_bdn_MAPVentureMember_bd93a324-ec08-407e-9380-28d29e92ae51" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_d068beb1-0162-41db-84a1-3a3df89ea155" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_089e3649-0bd8-4513-ad82-03a9fa3df8e9" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_d068beb1-0162-41db-84a1-3a3df89ea155" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_d068beb1-0162-41db-84a1-3a3df89ea155_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_d068beb1-0162-41db-84a1-3a3df89ea155" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_d068beb1-0162-41db-84a1-3a3df89ea155_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_069d6b8c-7f94-4700-9b99-9101b1b0d1ea" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_d068beb1-0162-41db-84a1-3a3df89ea155" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_069d6b8c-7f94-4700-9b99-9101b1b0d1ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_9851abae-67cd-48e7-be3c-f3c1a65376b1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_069d6b8c-7f94-4700-9b99-9101b1b0d1ea" xlink:to="loc_us-gaap_SecuredDebtMember_9851abae-67cd-48e7-be3c-f3c1a65376b1" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/INTANGIBLEASSETSANDLIABILITIESSummaryofIntangibleAssetsandLiabilitiesDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#INTANGIBLEASSETSANDLIABILITIESSummaryofIntangibleAssetsandLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/INTANGIBLEASSETSANDLIABILITIESSummaryofIntangibleAssetsandLiabilitiesDetails" xlink:type="extended" id="i18957c0561af4368b8c523b2902bdc11_INTANGIBLEASSETSANDLIABILITIESSummaryofIntangibleAssetsandLiabilitiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_539230cb-7a48-4661-9ff6-b321ff88dd4b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_c78453de-027c-48b8-8398-24baf53f0eb9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_539230cb-7a48-4661-9ff6-b321ff88dd4b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_c78453de-027c-48b8-8398-24baf53f0eb9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_3991ba20-3e9a-4ccd-8dd6-3d66cc13aaeb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_539230cb-7a48-4661-9ff6-b321ff88dd4b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_3991ba20-3e9a-4ccd-8dd6-3d66cc13aaeb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_712ad0af-18fa-4282-91aa-fb24e9aafcb8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_539230cb-7a48-4661-9ff6-b321ff88dd4b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_712ad0af-18fa-4282-91aa-fb24e9aafcb8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BelowMarketLeaseGross_247fa49c-1056-4f36-a9a9-a7b5572cda59" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BelowMarketLeaseGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_539230cb-7a48-4661-9ff6-b321ff88dd4b" xlink:to="loc_us-gaap_BelowMarketLeaseGross_247fa49c-1056-4f36-a9a9-a7b5572cda59" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BelowMarketLeaseAccumulatedAmortization_a4b31bfa-f27c-4439-a2be-ea0453027b92" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BelowMarketLeaseAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_539230cb-7a48-4661-9ff6-b321ff88dd4b" xlink:to="loc_us-gaap_BelowMarketLeaseAccumulatedAmortization_a4b31bfa-f27c-4439-a2be-ea0453027b92" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BelowMarketLeaseNet_cbf10581-0347-4a71-953b-2392e3cb1df2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BelowMarketLeaseNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_539230cb-7a48-4661-9ff6-b321ff88dd4b" xlink:to="loc_us-gaap_BelowMarketLeaseNet_cbf10581-0347-4a71-953b-2392e3cb1df2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_5239e1de-4246-4946-8e5a-778b7784be4e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_539230cb-7a48-4661-9ff6-b321ff88dd4b" xlink:to="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_5239e1de-4246-4946-8e5a-778b7784be4e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_09c28ad2-560a-468b-b9ad-47ee30591a79" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_5239e1de-4246-4946-8e5a-778b7784be4e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_09c28ad2-560a-468b-b9ad-47ee30591a79" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_09c28ad2-560a-468b-b9ad-47ee30591a79_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_09c28ad2-560a-468b-b9ad-47ee30591a79" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_09c28ad2-560a-468b-b9ad-47ee30591a79_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_82d941fd-8f7f-4858-959a-0516282e57d3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_09c28ad2-560a-468b-b9ad-47ee30591a79" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_82d941fd-8f7f-4858-959a-0516282e57d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeasesAcquiredInPlaceMember_9e21ae67-777f-4b9e-9305-867fc322f400" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LeasesAcquiredInPlaceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_82d941fd-8f7f-4858-959a-0516282e57d3" xlink:to="loc_us-gaap_LeasesAcquiredInPlaceMember_9e21ae67-777f-4b9e-9305-867fc322f400" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_e1e7b3d4-2d98-4cdc-8e94-fa5a137694f7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_82d941fd-8f7f-4858-959a-0516282e57d3" xlink:to="loc_us-gaap_CustomerRelationshipsMember_e1e7b3d4-2d98-4cdc-8e94-fa5a137694f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AboveMarketLeasesMember_73931ba1-f8c6-4608-add3-93f6a5e356a9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AboveMarketLeasesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_82d941fd-8f7f-4858-959a-0516282e57d3" xlink:to="loc_us-gaap_AboveMarketLeasesMember_73931ba1-f8c6-4608-add3-93f6a5e356a9" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/DEBTOBLIGATIONSScheduleofConsolidatedDebtObligationsOutstandingDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#DEBTOBLIGATIONSScheduleofConsolidatedDebtObligationsOutstandingDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/DEBTOBLIGATIONSScheduleofConsolidatedDebtObligationsOutstandingDetails" xlink:type="extended" id="ia01c80071f3e435aa96be24bb42ab63c_DEBTOBLIGATIONSScheduleofConsolidatedDebtObligationsOutstandingDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_0f91aa9a-b740-43a7-927e-5fb6bc6cc48d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_ConsolidatedDebtObligationsAbstract_8d124ef5-6cd8-47c3-9e42-24d5d051023f" xlink:href="bdn-20230630.xsd#bdn_ConsolidatedDebtObligationsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0f91aa9a-b740-43a7-927e-5fb6bc6cc48d" xlink:to="loc_bdn_ConsolidatedDebtObligationsAbstract_8d124ef5-6cd8-47c3-9e42-24d5d051023f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_b94b5826-d244-4328-af34-4b60f3dc99cb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_ConsolidatedDebtObligationsAbstract_8d124ef5-6cd8-47c3-9e42-24d5d051023f" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_b94b5826-d244-4328-af34-4b60f3dc99cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_d780b531-0684-474a-a18a-d53777ff8457" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_ConsolidatedDebtObligationsAbstract_8d124ef5-6cd8-47c3-9e42-24d5d051023f" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_d780b531-0684-474a-a18a-d53777ff8457" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_3ea25751-561c-4990-a196-9f11ec73c807" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_ConsolidatedDebtObligationsAbstract_8d124ef5-6cd8-47c3-9e42-24d5d051023f" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_3ea25751-561c-4990-a196-9f11ec73c807" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet_afc07f6b-5591-4c61-b661-bd8f2dd3f89e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_ConsolidatedDebtObligationsAbstract_8d124ef5-6cd8-47c3-9e42-24d5d051023f" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet_afc07f6b-5591-4c61-b661-bd8f2dd3f89e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_10d41925-0965-452b-928f-b399dc07e396" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_ConsolidatedDebtObligationsAbstract_8d124ef5-6cd8-47c3-9e42-24d5d051023f" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_10d41925-0965-452b-928f-b399dc07e396" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_58bcd337-df1e-4a33-ada0-7cec2356fb13" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_ConsolidatedDebtObligationsAbstract_8d124ef5-6cd8-47c3-9e42-24d5d051023f" xlink:to="loc_us-gaap_LongTermDebt_58bcd337-df1e-4a33-ada0-7cec2356fb13" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_a5aecc6f-e545-44d2-8e1b-e3ca561b0b0b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_ConsolidatedDebtObligationsAbstract_8d124ef5-6cd8-47c3-9e42-24d5d051023f" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_a5aecc6f-e545-44d2-8e1b-e3ca561b0b0b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_819c0ff3-6932-4b88-9b62-715a5d6cc841" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_ConsolidatedDebtObligationsAbstract_8d124ef5-6cd8-47c3-9e42-24d5d051023f" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_819c0ff3-6932-4b88-9b62-715a5d6cc841" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_DebtInstrumentExtensionPeriod_28b9e3f0-d89d-44d4-a347-336c00c421dd" xlink:href="bdn-20230630.xsd#bdn_DebtInstrumentExtensionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_ConsolidatedDebtObligationsAbstract_8d124ef5-6cd8-47c3-9e42-24d5d051023f" xlink:to="loc_bdn_DebtInstrumentExtensionPeriod_28b9e3f0-d89d-44d4-a347-336c00c421dd" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfUnsecuredDebt_1d6d85a6-ea24-4293-a7c8-b7f1f73cf6fb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RepaymentsOfUnsecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_ConsolidatedDebtObligationsAbstract_8d124ef5-6cd8-47c3-9e42-24d5d051023f" xlink:to="loc_us-gaap_RepaymentsOfUnsecuredDebt_1d6d85a6-ea24-4293-a7c8-b7f1f73cf6fb" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRepurchaseAmount_8ecf92f1-0d47-48b5-af38-0bb64153e90a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRepurchaseAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_ConsolidatedDebtObligationsAbstract_8d124ef5-6cd8-47c3-9e42-24d5d051023f" xlink:to="loc_us-gaap_DebtInstrumentRepurchaseAmount_8ecf92f1-0d47-48b5-af38-0bb64153e90a" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPayableCurrentAndNoncurrent_2a7d4af0-db20-43c2-9073-df762ed52420" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestPayableCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_ConsolidatedDebtObligationsAbstract_8d124ef5-6cd8-47c3-9e42-24d5d051023f" xlink:to="loc_us-gaap_InterestPayableCurrentAndNoncurrent_2a7d4af0-db20-43c2-9073-df762ed52420" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_d02c22c7-05dd-4be4-94ad-1a3fdd7e6be9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0f91aa9a-b740-43a7-927e-5fb6bc6cc48d" xlink:to="loc_us-gaap_DebtInstrumentTable_d02c22c7-05dd-4be4-94ad-1a3fdd7e6be9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_4a85fda1-1799-4282-b4fd-0cb56d9c2169" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_d02c22c7-05dd-4be4-94ad-1a3fdd7e6be9" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_4a85fda1-1799-4282-b4fd-0cb56d9c2169" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_4a85fda1-1799-4282-b4fd-0cb56d9c2169_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_4a85fda1-1799-4282-b4fd-0cb56d9c2169" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_4a85fda1-1799-4282-b4fd-0cb56d9c2169_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_09bfdcca-1ed3-4bd3-83be-1b1fe15785a0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_4a85fda1-1799-4282-b4fd-0cb56d9c2169" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_09bfdcca-1ed3-4bd3-83be-1b1fe15785a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_86bac672-02bd-4e12-aa12-3633d5ac7812" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_09bfdcca-1ed3-4bd3-83be-1b1fe15785a0" xlink:to="loc_us-gaap_SecuredDebtMember_86bac672-02bd-4e12-aa12-3633d5ac7812" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_57ebab38-0ff5-4017-8205-43c1a647f9ef" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_09bfdcca-1ed3-4bd3-83be-1b1fe15785a0" xlink:to="loc_us-gaap_UnsecuredDebtMember_57ebab38-0ff5-4017-8205-43c1a647f9ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_55855882-dbcd-4c90-9955-52cc5a817567" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_d02c22c7-05dd-4be4-94ad-1a3fdd7e6be9" xlink:to="loc_us-gaap_DebtInstrumentAxis_55855882-dbcd-4c90-9955-52cc5a817567" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_55855882-dbcd-4c90-9955-52cc5a817567_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_55855882-dbcd-4c90-9955-52cc5a817567" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_55855882-dbcd-4c90-9955-52cc5a817567_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_8fa66ce5-a23f-46ff-98eb-11883d729dfe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_55855882-dbcd-4c90-9955-52cc5a817567" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_8fa66ce5-a23f-46ff-98eb-11883d729dfe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_SecuredTermLoanDue2028Member_946ac36f-df9a-4f3e-a7e5-c110d17a076b" xlink:href="bdn-20230630.xsd#bdn_SecuredTermLoanDue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8fa66ce5-a23f-46ff-98eb-11883d729dfe" xlink:to="loc_bdn_SecuredTermLoanDue2028Member_946ac36f-df9a-4f3e-a7e5-c110d17a076b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_A600MillionUnsecuredCreditFacilityMember_b92f2f78-00ea-426b-803d-dd4772638940" xlink:href="bdn-20230630.xsd#bdn_A600MillionUnsecuredCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8fa66ce5-a23f-46ff-98eb-11883d729dfe" xlink:to="loc_bdn_A600MillionUnsecuredCreditFacilityMember_b92f2f78-00ea-426b-803d-dd4772638940" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_TermLoanMember_f96403c5-d311-4476-9cae-9c364caaec64" xlink:href="bdn-20230630.xsd#bdn_TermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8fa66ce5-a23f-46ff-98eb-11883d729dfe" xlink:to="loc_bdn_TermLoanMember_f96403c5-d311-4476-9cae-9c364caaec64" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_A700MillionTermLoanMember_154cdbf7-ce2d-49bd-886d-1cb8955bb485" xlink:href="bdn-20230630.xsd#bdn_A700MillionTermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8fa66ce5-a23f-46ff-98eb-11883d729dfe" xlink:to="loc_bdn_A700MillionTermLoanMember_154cdbf7-ce2d-49bd-886d-1cb8955bb485" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_Note2023Member_635dc69e-de6e-4a08-ad1f-57f5996badab" xlink:href="bdn-20230630.xsd#bdn_Note2023Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8fa66ce5-a23f-46ff-98eb-11883d729dfe" xlink:to="loc_bdn_Note2023Member_635dc69e-de6e-4a08-ad1f-57f5996badab" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_Note2024Member_b214c632-40d3-46db-a12e-9d0522578ebe" xlink:href="bdn-20230630.xsd#bdn_Note2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8fa66ce5-a23f-46ff-98eb-11883d729dfe" xlink:to="loc_bdn_Note2024Member_b214c632-40d3-46db-a12e-9d0522578ebe" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_Note2027Member_3f043a09-bf7a-4926-a41f-d45e475e2c90" xlink:href="bdn-20230630.xsd#bdn_Note2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8fa66ce5-a23f-46ff-98eb-11883d729dfe" xlink:to="loc_bdn_Note2027Member_3f043a09-bf7a-4926-a41f-d45e475e2c90" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_Note2028Member_5a14feed-0565-413e-b6a4-6a7a35402bde" xlink:href="bdn-20230630.xsd#bdn_Note2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8fa66ce5-a23f-46ff-98eb-11883d729dfe" xlink:to="loc_bdn_Note2028Member_5a14feed-0565-413e-b6a4-6a7a35402bde" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_Note2029Member_71c69c12-92c5-400b-8ffd-0847471b3490" xlink:href="bdn-20230630.xsd#bdn_Note2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8fa66ce5-a23f-46ff-98eb-11883d729dfe" xlink:to="loc_bdn_Note2029Member_71c69c12-92c5-400b-8ffd-0847471b3490" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_IndentureIAPreferredTrustIMember_f1d5148a-ca15-4d15-a90c-6479b71893b2" xlink:href="bdn-20230630.xsd#bdn_IndentureIAPreferredTrustIMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8fa66ce5-a23f-46ff-98eb-11883d729dfe" xlink:to="loc_bdn_IndentureIAPreferredTrustIMember_f1d5148a-ca15-4d15-a90c-6479b71893b2" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_IndentureIBPreferredTrustIMember_b9cba235-c768-44fc-8e31-0ef77250a4b3" xlink:href="bdn-20230630.xsd#bdn_IndentureIBPreferredTrustIMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8fa66ce5-a23f-46ff-98eb-11883d729dfe" xlink:to="loc_bdn_IndentureIBPreferredTrustIMember_b9cba235-c768-44fc-8e31-0ef77250a4b3" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_IndentureIIPreferredTrustIiMember_21117de0-0ad5-46aa-bc18-74c9d312c87a" xlink:href="bdn-20230630.xsd#bdn_IndentureIIPreferredTrustIiMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8fa66ce5-a23f-46ff-98eb-11883d729dfe" xlink:to="loc_bdn_IndentureIIPreferredTrustIiMember_21117de0-0ad5-46aa-bc18-74c9d312c87a" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_428be688-2a04-4a53-8e80-5cc8e66df679" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_d02c22c7-05dd-4be4-94ad-1a3fdd7e6be9" xlink:to="loc_us-gaap_VariableRateAxis_428be688-2a04-4a53-8e80-5cc8e66df679" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_428be688-2a04-4a53-8e80-5cc8e66df679_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_428be688-2a04-4a53-8e80-5cc8e66df679" xlink:to="loc_us-gaap_VariableRateDomain_428be688-2a04-4a53-8e80-5cc8e66df679_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_d753392b-29ed-4329-bcdc-b1f27870733d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_428be688-2a04-4a53-8e80-5cc8e66df679" xlink:to="loc_us-gaap_VariableRateDomain_d753392b-29ed-4329-bcdc-b1f27870733d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_5d1a011c-0d3f-4977-b370-ad52a32c4285" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_d753392b-29ed-4329-bcdc-b1f27870733d" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_5d1a011c-0d3f-4977-b370-ad52a32c4285" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_LondonInterbankOfferedRateMember_84efb8c9-4474-485d-b5bc-0f3be47c80e5" xlink:href="bdn-20230630.xsd#bdn_LondonInterbankOfferedRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_d753392b-29ed-4329-bcdc-b1f27870733d" xlink:to="loc_bdn_LondonInterbankOfferedRateMember_84efb8c9-4474-485d-b5bc-0f3be47c80e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_DailySOFRAdjustmentMember_b31012af-e700-4687-b76e-9895f0acfbf4" xlink:href="bdn-20230630.xsd#bdn_DailySOFRAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_d753392b-29ed-4329-bcdc-b1f27870733d" xlink:to="loc_bdn_DailySOFRAdjustmentMember_b31012af-e700-4687-b76e-9895f0acfbf4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_e901509d-f873-4741-a650-4ef5ebecfcdd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_d02c22c7-05dd-4be4-94ad-1a3fdd7e6be9" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_e901509d-f873-4741-a650-4ef5ebecfcdd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_e901509d-f873-4741-a650-4ef5ebecfcdd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_e901509d-f873-4741-a650-4ef5ebecfcdd" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_e901509d-f873-4741-a650-4ef5ebecfcdd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_03000af2-58fb-47b6-b0cb-379b878acede" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_e901509d-f873-4741-a650-4ef5ebecfcdd" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_03000af2-58fb-47b6-b0cb-379b878acede" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_03df0a32-00ea-4b19-aec5-cdff3e8ebe77" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_03000af2-58fb-47b6-b0cb-379b878acede" xlink:to="loc_us-gaap_SubsequentEventMember_03df0a32-00ea-4b19-aec5-cdff3e8ebe77" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/DEBTOBLIGATIONSNarrativeDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#DEBTOBLIGATIONSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/DEBTOBLIGATIONSNarrativeDetails" xlink:type="extended" id="i7f73a6e956fa4b4f90657634dbecd33b_DEBTOBLIGATIONSNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_ffd8f646-7321-4957-ae97-7ba95a727024" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_110086aa-04d6-4e4e-89cf-f2de05a54e4f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ffd8f646-7321-4957-ae97-7ba95a727024" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_110086aa-04d6-4e4e-89cf-f2de05a54e4f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_4d8efb11-5636-4cc2-b1fc-8f073acc29b9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ffd8f646-7321-4957-ae97-7ba95a727024" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_4d8efb11-5636-4cc2-b1fc-8f073acc29b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_d7f15101-987a-4192-ba7b-5ac228e5ae3b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtWeightedAverageInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ffd8f646-7321-4957-ae97-7ba95a727024" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_d7f15101-987a-4192-ba7b-5ac228e5ae3b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseBorrowings_6b28361b-fb27-4091-ab89-862c5a0b57fa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpenseBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ffd8f646-7321-4957-ae97-7ba95a727024" xlink:to="loc_us-gaap_InterestExpenseBorrowings_6b28361b-fb27-4091-ab89-862c5a0b57fa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_NumberOfWhollyOwnedSubsidiariesParticipatingInALoanAgreement_81cf74cd-3ebf-4c50-a5ff-162fb1b0ae14" xlink:href="bdn-20230630.xsd#bdn_NumberOfWhollyOwnedSubsidiariesParticipatingInALoanAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ffd8f646-7321-4957-ae97-7ba95a727024" xlink:to="loc_bdn_NumberOfWhollyOwnedSubsidiariesParticipatingInALoanAgreement_81cf74cd-3ebf-4c50-a5ff-162fb1b0ae14" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_DebtInstrumentNumberOfOperatingPropertiesSecuringTheDebt_06f28860-d66a-425e-b8d8-d37a07df8cb7" xlink:href="bdn-20230630.xsd#bdn_DebtInstrumentNumberOfOperatingPropertiesSecuringTheDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ffd8f646-7321-4957-ae97-7ba95a727024" xlink:to="loc_bdn_DebtInstrumentNumberOfOperatingPropertiesSecuringTheDebt_06f28860-d66a-425e-b8d8-d37a07df8cb7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_e799e64c-623a-4215-bf7f-ec070d33a119" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ffd8f646-7321-4957-ae97-7ba95a727024" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_e799e64c-623a-4215-bf7f-ec070d33a119" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_c60811a2-f385-4163-a4b6-6f063e99d246" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ffd8f646-7321-4957-ae97-7ba95a727024" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_c60811a2-f385-4163-a4b6-6f063e99d246" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_828af398-4688-42e3-a782-73d0506b729b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ffd8f646-7321-4957-ae97-7ba95a727024" xlink:to="loc_us-gaap_DebtInstrumentTerm_828af398-4688-42e3-a782-73d0506b729b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_DebtInstrumentExtensionTerm_5ce542ab-75ca-40ba-b2a1-f82d093fa5c5" xlink:href="bdn-20230630.xsd#bdn_DebtInstrumentExtensionTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ffd8f646-7321-4957-ae97-7ba95a727024" xlink:to="loc_bdn_DebtInstrumentExtensionTerm_5ce542ab-75ca-40ba-b2a1-f82d093fa5c5" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_428b7dff-9f0e-4daf-a35c-be8cf850c316" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ffd8f646-7321-4957-ae97-7ba95a727024" xlink:to="loc_us-gaap_DebtInstrumentTable_428b7dff-9f0e-4daf-a35c-be8cf850c316" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_ef062afd-933e-4aa6-92f3-30e4f99d4f20" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_428b7dff-9f0e-4daf-a35c-be8cf850c316" xlink:to="loc_us-gaap_DebtInstrumentAxis_ef062afd-933e-4aa6-92f3-30e4f99d4f20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_ef062afd-933e-4aa6-92f3-30e4f99d4f20_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_ef062afd-933e-4aa6-92f3-30e4f99d4f20" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_ef062afd-933e-4aa6-92f3-30e4f99d4f20_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9fbae90f-bc1b-477f-8161-b099a41a25c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_ef062afd-933e-4aa6-92f3-30e4f99d4f20" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_9fbae90f-bc1b-477f-8161-b099a41a25c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_A600MillionUnsecuredCreditFacilityMember_b29b6443-df45-4ea9-b98a-4bdfbd1978bb" xlink:href="bdn-20230630.xsd#bdn_A600MillionUnsecuredCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_9fbae90f-bc1b-477f-8161-b099a41a25c2" xlink:to="loc_bdn_A600MillionUnsecuredCreditFacilityMember_b29b6443-df45-4ea9-b98a-4bdfbd1978bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_SecuredFacilityMember_feb3f96a-6ed8-489e-9f16-4c4136495e25" xlink:href="bdn-20230630.xsd#bdn_SecuredFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_9fbae90f-bc1b-477f-8161-b099a41a25c2" xlink:to="loc_bdn_SecuredFacilityMember_feb3f96a-6ed8-489e-9f16-4c4136495e25" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_A700MillionTermLoanMember_a0c4104e-e60e-4012-bed9-7e6c84ee9b1e" xlink:href="bdn-20230630.xsd#bdn_A700MillionTermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_9fbae90f-bc1b-477f-8161-b099a41a25c2" xlink:to="loc_bdn_A700MillionTermLoanMember_a0c4104e-e60e-4012-bed9-7e6c84ee9b1e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_ec1c462e-5318-41b0-9ba6-8986a0e03fff" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_428b7dff-9f0e-4daf-a35c-be8cf850c316" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_ec1c462e-5318-41b0-9ba6-8986a0e03fff" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_ec1c462e-5318-41b0-9ba6-8986a0e03fff_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ec1c462e-5318-41b0-9ba6-8986a0e03fff" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_ec1c462e-5318-41b0-9ba6-8986a0e03fff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2753f103-2337-434d-8afe-afc25cb2abdd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ec1c462e-5318-41b0-9ba6-8986a0e03fff" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2753f103-2337-434d-8afe-afc25cb2abdd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_39738ddc-e64b-4739-8bd1-f71901e8a1ff" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_2753f103-2337-434d-8afe-afc25cb2abdd" xlink:to="loc_us-gaap_UnsecuredDebtMember_39738ddc-e64b-4739-8bd1-f71901e8a1ff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_a71702e1-4b14-46ab-b6f4-f8b8808286fe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_428b7dff-9f0e-4daf-a35c-be8cf850c316" xlink:to="loc_us-gaap_VariableRateAxis_a71702e1-4b14-46ab-b6f4-f8b8808286fe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_a71702e1-4b14-46ab-b6f4-f8b8808286fe_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_a71702e1-4b14-46ab-b6f4-f8b8808286fe" xlink:to="loc_us-gaap_VariableRateDomain_a71702e1-4b14-46ab-b6f4-f8b8808286fe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_453cb99c-810e-45c1-ab42-4ac925c0cc64" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_a71702e1-4b14-46ab-b6f4-f8b8808286fe" xlink:to="loc_us-gaap_VariableRateDomain_453cb99c-810e-45c1-ab42-4ac925c0cc64" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_SecuredOvernightFinancingRateSOFROvernightIndexSwapRateBeforeAdjustmentMember_b4ae3f65-1db9-4d4a-a50c-4ff8545e756c" xlink:href="bdn-20230630.xsd#bdn_SecuredOvernightFinancingRateSOFROvernightIndexSwapRateBeforeAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_453cb99c-810e-45c1-ab42-4ac925c0cc64" xlink:to="loc_bdn_SecuredOvernightFinancingRateSOFROvernightIndexSwapRateBeforeAdjustmentMember_b4ae3f65-1db9-4d4a-a50c-4ff8545e756c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_DailySOFRAdjustmentMember_90b4af36-c7e2-4bcd-bbb3-4924f27bb64a" xlink:href="bdn-20230630.xsd#bdn_DailySOFRAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_453cb99c-810e-45c1-ab42-4ac925c0cc64" xlink:to="loc_bdn_DailySOFRAdjustmentMember_90b4af36-c7e2-4bcd-bbb3-4924f27bb64a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_c796600a-d615-4c5d-a5a1-ee52486d06de" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_428b7dff-9f0e-4daf-a35c-be8cf850c316" xlink:to="loc_us-gaap_CreditFacilityAxis_c796600a-d615-4c5d-a5a1-ee52486d06de" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_c796600a-d615-4c5d-a5a1-ee52486d06de_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_c796600a-d615-4c5d-a5a1-ee52486d06de" xlink:to="loc_us-gaap_CreditFacilityDomain_c796600a-d615-4c5d-a5a1-ee52486d06de_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_5ed9ef97-30b7-42af-95f1-be0a9112caa5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_c796600a-d615-4c5d-a5a1-ee52486d06de" xlink:to="loc_us-gaap_CreditFacilityDomain_5ed9ef97-30b7-42af-95f1-be0a9112caa5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_26efdb14-90f0-45ed-b6f8-ddf51d6f4bc5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5ed9ef97-30b7-42af-95f1-be0a9112caa5" xlink:to="loc_us-gaap_SecuredDebtMember_26efdb14-90f0-45ed-b6f8-ddf51d6f4bc5" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/FAIRVALUEOFFINANCIALINSTRUMENTSFinancialInstrumentsforwhichEstimatesofFairValueDifferfromCarryingAmountsDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#FAIRVALUEOFFINANCIALINSTRUMENTSFinancialInstrumentsforwhichEstimatesofFairValueDifferfromCarryingAmountsDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/FAIRVALUEOFFINANCIALINSTRUMENTSFinancialInstrumentsforwhichEstimatesofFairValueDifferfromCarryingAmountsDetails" xlink:type="extended" id="i45b74f542ca544568d7b9aa12713879f_FAIRVALUEOFFINANCIALINSTRUMENTSFinancialInstrumentsforwhichEstimatesofFairValueDifferfromCarryingAmountsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_64acc167-dfcb-4f11-a559-19161e089779" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayable_706c874f-d33d-4ce5-9bf0-69746fc0538c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NotesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_64acc167-dfcb-4f11-a559-19161e089779" xlink:to="loc_us-gaap_NotesPayable_706c874f-d33d-4ce5-9bf0-69746fc0538c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansPayable_b858a42f-32a6-40bc-83c6-7772029bf2aa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LoansPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_64acc167-dfcb-4f11-a559-19161e089779" xlink:to="loc_us-gaap_LoansPayable_b858a42f-32a6-40bc-83c6-7772029bf2aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebt_e96e8b6a-a5db-4bb2-a15e-34f7127fdfda" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_64acc167-dfcb-4f11-a559-19161e089779" xlink:to="loc_us-gaap_SecuredDebt_e96e8b6a-a5db-4bb2-a15e-34f7127fdfda" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFairValue_a5db040d-7561-4c7b-b6d7-3a29f15c6835" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_64acc167-dfcb-4f11-a559-19161e089779" xlink:to="loc_us-gaap_DebtInstrumentFairValue_a5db040d-7561-4c7b-b6d7-3a29f15c6835" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_21e39694-a2c4-492b-859a-576c06c3e80b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_64acc167-dfcb-4f11-a559-19161e089779" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_21e39694-a2c4-492b-859a-576c06c3e80b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_d5a98614-55e4-42aa-a9e9-7e682a1ee6be" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_64acc167-dfcb-4f11-a559-19161e089779" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_d5a98614-55e4-42aa-a9e9-7e682a1ee6be" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_03db73c8-d007-4d09-b51f-01ac7ee5ad5d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_d5a98614-55e4-42aa-a9e9-7e682a1ee6be" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_03db73c8-d007-4d09-b51f-01ac7ee5ad5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_03db73c8-d007-4d09-b51f-01ac7ee5ad5d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_03db73c8-d007-4d09-b51f-01ac7ee5ad5d" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_03db73c8-d007-4d09-b51f-01ac7ee5ad5d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_2442f1b8-b2d7-42b9-8854-adab887162ad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_03db73c8-d007-4d09-b51f-01ac7ee5ad5d" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_2442f1b8-b2d7-42b9-8854-adab887162ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_07be7541-0323-474d-b90e-fe5cecb3a8e8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_2442f1b8-b2d7-42b9-8854-adab887162ad" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_07be7541-0323-474d-b90e-fe5cecb3a8e8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_653f5faf-b74e-4876-8f66-1679eb069548" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_07be7541-0323-474d-b90e-fe5cecb3a8e8" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_653f5faf-b74e-4876-8f66-1679eb069548" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_f56d25e2-38eb-40eb-b862-63f5f23637c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_07be7541-0323-474d-b90e-fe5cecb3a8e8" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_f56d25e2-38eb-40eb-b862-63f5f23637c8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_d017dfff-4bf7-4219-bc69-2e7421868eda" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_d5a98614-55e4-42aa-a9e9-7e682a1ee6be" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_d017dfff-4bf7-4219-bc69-2e7421868eda" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_d017dfff-4bf7-4219-bc69-2e7421868eda_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_d017dfff-4bf7-4219-bc69-2e7421868eda" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_d017dfff-4bf7-4219-bc69-2e7421868eda_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_fbfff4a6-b90b-44fb-b7c7-c7378d5b5321" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_d017dfff-4bf7-4219-bc69-2e7421868eda" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_fbfff4a6-b90b-44fb-b7c7-c7378d5b5321" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_25023dd5-4d3e-4eeb-9b95-a37b746e70a8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_fbfff4a6-b90b-44fb-b7c7-c7378d5b5321" xlink:to="loc_us-gaap_UnsecuredDebtMember_25023dd5-4d3e-4eeb-9b95-a37b746e70a8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_VariableRateDebtMember_319f8abd-7174-4ba9-a3e2-1a8f34335956" xlink:href="bdn-20230630.xsd#bdn_VariableRateDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_fbfff4a6-b90b-44fb-b7c7-c7378d5b5321" xlink:to="loc_bdn_VariableRateDebtMember_319f8abd-7174-4ba9-a3e2-1a8f34335956" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_6736cd20-d6a9-43f1-b91a-02890fb0a990" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_fbfff4a6-b90b-44fb-b7c7-c7378d5b5321" xlink:to="loc_us-gaap_SecuredDebtMember_6736cd20-d6a9-43f1-b91a-02890fb0a990" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/DERIVATIVEFINANCIALINSTRUMENTSDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#DERIVATIVEFINANCIALINSTRUMENTSDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/DERIVATIVEFINANCIALINSTRUMENTSDetails" xlink:type="extended" id="ia5c3f5ef6f5846b1b74400a3d6f93569_DERIVATIVEFINANCIALINSTRUMENTSDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_476f5278-f191-490b-9bd7-cc6f5543800c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativesFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_dbcbce08-ad21-4f38-a32a-7824264d484f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_476f5278-f191-490b-9bd7-cc6f5543800c" xlink:to="loc_us-gaap_DerivativeNotionalAmount_dbcbce08-ad21-4f38-a32a-7824264d484f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFixedInterestRate_d3663e99-7663-4e4e-84fa-7b95527c842a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFixedInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_476f5278-f191-490b-9bd7-cc6f5543800c" xlink:to="loc_us-gaap_DerivativeFixedInterestRate_d3663e99-7663-4e4e-84fa-7b95527c842a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateFairValueHedgeAssetAtFairValue_33cb0267-eff6-478e-80ee-6e206b35136c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateFairValueHedgeAssetAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_476f5278-f191-490b-9bd7-cc6f5543800c" xlink:to="loc_us-gaap_InterestRateFairValueHedgeAssetAtFairValue_33cb0267-eff6-478e-80ee-6e206b35136c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_2ee3ff8b-37ef-498e-b886-8925621b0887" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_476f5278-f191-490b-9bd7-cc6f5543800c" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_2ee3ff8b-37ef-498e-b886-8925621b0887" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_6aaeba0a-e2b6-437c-94e6-0135997aa65e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_2ee3ff8b-37ef-498e-b886-8925621b0887" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_6aaeba0a-e2b6-437c-94e6-0135997aa65e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_6aaeba0a-e2b6-437c-94e6-0135997aa65e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_6aaeba0a-e2b6-437c-94e6-0135997aa65e" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_6aaeba0a-e2b6-437c-94e6-0135997aa65e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_51da3e3c-707a-4a77-a357-9604e32038c0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_6aaeba0a-e2b6-437c-94e6-0135997aa65e" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_51da3e3c-707a-4a77-a357-9604e32038c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_A2868InterestRateSwapMaturingOctober82022Member_3eba9cca-e35b-478f-8dd7-134c81c6f7da" xlink:href="bdn-20230630.xsd#bdn_A2868InterestRateSwapMaturingOctober82022Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_51da3e3c-707a-4a77-a357-9604e32038c0" xlink:to="loc_bdn_A2868InterestRateSwapMaturingOctober82022Member_3eba9cca-e35b-478f-8dd7-134c81c6f7da" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_72c8044d-3656-4084-94c0-38657d8bc334" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_2ee3ff8b-37ef-498e-b886-8925621b0887" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_72c8044d-3656-4084-94c0-38657d8bc334" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_72c8044d-3656-4084-94c0-38657d8bc334_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_72c8044d-3656-4084-94c0-38657d8bc334" xlink:to="loc_us-gaap_HedgingRelationshipDomain_72c8044d-3656-4084-94c0-38657d8bc334_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_effcdbe0-a801-4577-8dd6-87d9d405fb14" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_72c8044d-3656-4084-94c0-38657d8bc334" xlink:to="loc_us-gaap_HedgingRelationshipDomain_effcdbe0-a801-4577-8dd6-87d9d405fb14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_be0a89b6-7d7c-4f0d-a3ec-7a369d0b0bb5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashFlowHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_effcdbe0-a801-4577-8dd6-87d9d405fb14" xlink:to="loc_us-gaap_CashFlowHedgingMember_be0a89b6-7d7c-4f0d-a3ec-7a369d0b0bb5" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/BENEFICIARIESEQUITYOFTHEPARENTCOMPANYNarrativeDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#BENEFICIARIESEQUITYOFTHEPARENTCOMPANYNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/BENEFICIARIESEQUITYOFTHEPARENTCOMPANYNarrativeDetails" xlink:type="extended" id="i9ee6cff02a67438f9894132718fff1cc_BENEFICIARIESEQUITYOFTHEPARENTCOMPANYNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_3faa6653-4534-4267-b36d-8927863de7b8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_5e1e102b-163a-4469-86e9-9aeb5b231267" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_3faa6653-4534-4267-b36d-8927863de7b8" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_5e1e102b-163a-4469-86e9-9aeb5b231267" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_31f5d223-2ab8-4863-877b-aa58d050cb2d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_3faa6653-4534-4267-b36d-8927863de7b8" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_31f5d223-2ab8-4863-877b-aa58d050cb2d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareCashPaid_2eb451e3-5554-4aa8-a757-41ac596c016f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockDividendsPerShareCashPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_3faa6653-4534-4267-b36d-8927863de7b8" xlink:to="loc_us-gaap_CommonStockDividendsPerShareCashPaid_2eb451e3-5554-4aa8-a757-41ac596c016f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStock_078e8cca-681d-4a5e-8d89-01ec4ef10d3e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_3faa6653-4534-4267-b36d-8927863de7b8" xlink:to="loc_us-gaap_DividendsCommonStock_078e8cca-681d-4a5e-8d89-01ec4ef10d3e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_1975b0b7-02bc-47e7-9bc9-bb56bafa475a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_3faa6653-4534-4267-b36d-8927863de7b8" xlink:to="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_1975b0b7-02bc-47e7-9bc9-bb56bafa475a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_5e9e939c-926b-48c3-8a19-607c84e7a7e8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_3faa6653-4534-4267-b36d-8927863de7b8" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_5e9e939c-926b-48c3-8a19-607c84e7a7e8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_e676beb8-0a96-4f16-9243-f1ebb38a87f8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_3faa6653-4534-4267-b36d-8927863de7b8" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_e676beb8-0a96-4f16-9243-f1ebb38a87f8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_8f15b230-f673-4408-9036-bc6fdaf6c5f4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_e676beb8-0a96-4f16-9243-f1ebb38a87f8" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_8f15b230-f673-4408-9036-bc6fdaf6c5f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_8f15b230-f673-4408-9036-bc6fdaf6c5f4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_8f15b230-f673-4408-9036-bc6fdaf6c5f4" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_8f15b230-f673-4408-9036-bc6fdaf6c5f4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_16d6451c-113b-4096-b701-015868eeea11" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_8f15b230-f673-4408-9036-bc6fdaf6c5f4" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_16d6451c-113b-4096-b701-015868eeea11" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_RedeemableCommonLimitedPartnershipUnitsMember_b0f7a3db-3f9f-4877-8f8b-e5b8d059eb34" xlink:href="bdn-20230630.xsd#bdn_RedeemableCommonLimitedPartnershipUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_16d6451c-113b-4096-b701-015868eeea11" xlink:to="loc_bdn_RedeemableCommonLimitedPartnershipUnitsMember_b0f7a3db-3f9f-4877-8f8b-e5b8d059eb34" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/PARTNERSEQUITYOFTHEPARENTCOMPANYScheduleofNumberofUnitsandNetIncomeUsedtoCalculateBasicandDilutedEarningsPerCommonPartnershipUnitDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#PARTNERSEQUITYOFTHEPARENTCOMPANYScheduleofNumberofUnitsandNetIncomeUsedtoCalculateBasicandDilutedEarningsPerCommonPartnershipUnitDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/PARTNERSEQUITYOFTHEPARENTCOMPANYScheduleofNumberofUnitsandNetIncomeUsedtoCalculateBasicandDilutedEarningsPerCommonPartnershipUnitDetails" xlink:type="extended" id="id95353c57d16467e9f4aae4ab26ea370_PARTNERSEQUITYOFTHEPARENTCOMPANYScheduleofNumberofUnitsandNetIncomeUsedtoCalculateBasicandDilutedEarningsPerCommonPartnershipUnitDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_5269becc-c985-4272-85e0-2e417fd46401" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareReconciliationAbstract_a3fdd040-59db-4c14-b38f-bae14ed1aee1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareReconciliationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_5269becc-c985-4272-85e0-2e417fd46401" xlink:to="loc_us-gaap_EarningsPerShareReconciliationAbstract_a3fdd040-59db-4c14-b38f-bae14ed1aee1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_b5ab1084-5aa1-49ee-a3b0-8c8c9a42faf9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareReconciliationAbstract_a3fdd040-59db-4c14-b38f-bae14ed1aee1" xlink:to="loc_us-gaap_ProfitLoss_b5ab1084-5aa1-49ee-a3b0-8c8c9a42faf9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestInNetIncomeLossJointVenturePartnersRedeemable_944b2d8c-4b1b-44ae-abdf-b8b2673b592b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoncontrollingInterestInNetIncomeLossJointVenturePartnersRedeemable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareReconciliationAbstract_a3fdd040-59db-4c14-b38f-bae14ed1aee1" xlink:to="loc_us-gaap_NoncontrollingInterestInNetIncomeLossJointVenturePartnersRedeemable_944b2d8c-4b1b-44ae-abdf-b8b2673b592b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic_22fd1f2a-79d3-4b72-a607-4c285d3114a4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareReconciliationAbstract_a3fdd040-59db-4c14-b38f-bae14ed1aee1" xlink:to="loc_us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic_22fd1f2a-79d3-4b72-a607-4c285d3114a4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesDiluted_522ab443-b33c-4fe8-a722-11191c877f1a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareReconciliationAbstract_a3fdd040-59db-4c14-b38f-bae14ed1aee1" xlink:to="loc_us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesDiluted_522ab443-b33c-4fe8-a722-11191c877f1a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_NetIncomeLossAvailableToCommonUnitholdersBasic_54d6b07d-f04b-4c11-950e-ce955124222c" xlink:href="bdn-20230630.xsd#bdn_NetIncomeLossAvailableToCommonUnitholdersBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareReconciliationAbstract_a3fdd040-59db-4c14-b38f-bae14ed1aee1" xlink:to="loc_bdn_NetIncomeLossAvailableToCommonUnitholdersBasic_54d6b07d-f04b-4c11-950e-ce955124222c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_NetIncomeLossAvailableToCommonUnitHoldersDiluted_246ac7a8-cded-418f-a411-16854b66e8d1" xlink:href="bdn-20230630.xsd#bdn_NetIncomeLossAvailableToCommonUnitHoldersDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareReconciliationAbstract_a3fdd040-59db-4c14-b38f-bae14ed1aee1" xlink:to="loc_bdn_NetIncomeLossAvailableToCommonUnitHoldersDiluted_246ac7a8-cded-418f-a411-16854b66e8d1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_130b42a5-ec73-4896-ad65-ec209baf704f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_5269becc-c985-4272-85e0-2e417fd46401" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_130b42a5-ec73-4896-ad65-ec209baf704f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_67453c3f-4d12-4b32-8280-81d4ff506dfe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_130b42a5-ec73-4896-ad65-ec209baf704f" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_67453c3f-4d12-4b32-8280-81d4ff506dfe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_8367e237-0497-405b-9345-98d3e6497a47" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_130b42a5-ec73-4896-ad65-ec209baf704f" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_8367e237-0497-405b-9345-98d3e6497a47" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_ffad8fc5-1c17-4b02-8441-305377805ecc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_130b42a5-ec73-4896-ad65-ec209baf704f" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_ffad8fc5-1c17-4b02-8441-305377805ecc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_05e7f86c-ab96-435b-939b-66313d65220a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_5269becc-c985-4272-85e0-2e417fd46401" xlink:to="loc_us-gaap_EarningsPerShareAbstract_05e7f86c-ab96-435b-939b-66313d65220a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_89ed83c5-54b2-4fd4-a0a6-e652a44b365b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_05e7f86c-ab96-435b-939b-66313d65220a" xlink:to="loc_us-gaap_EarningsPerShareBasic_89ed83c5-54b2-4fd4-a0a6-e652a44b365b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_a91bc60d-ab46-44bb-b085-bcb13d472a70" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_05e7f86c-ab96-435b-939b-66313d65220a" xlink:to="loc_us-gaap_EarningsPerShareDiluted_a91bc60d-ab46-44bb-b085-bcb13d472a70" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_dd7c8ec6-2e1d-409e-937f-acf7c8adc9b7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_5269becc-c985-4272-85e0-2e417fd46401" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_dd7c8ec6-2e1d-409e-937f-acf7c8adc9b7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_d5a41f3f-e7c1-466b-803d-ad00c7bbb3b6" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_dd7c8ec6-2e1d-409e-937f-acf7c8adc9b7" xlink:to="loc_srt_ConsolidatedEntitiesAxis_d5a41f3f-e7c1-466b-803d-ad00c7bbb3b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_d5a41f3f-e7c1-466b-803d-ad00c7bbb3b6_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_d5a41f3f-e7c1-466b-803d-ad00c7bbb3b6" xlink:to="loc_srt_ConsolidatedEntitiesDomain_d5a41f3f-e7c1-466b-803d-ad00c7bbb3b6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_0668f5e3-b914-4fa7-a040-474657788b1e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_d5a41f3f-e7c1-466b-803d-ad00c7bbb3b6" xlink:to="loc_srt_ConsolidatedEntitiesDomain_0668f5e3-b914-4fa7-a040-474657788b1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember_767393f1-0cbf-4a60-a14d-0ea247eafcd6" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_0668f5e3-b914-4fa7-a040-474657788b1e" xlink:to="loc_srt_SubsidiariesMember_767393f1-0cbf-4a60-a14d-0ea247eafcd6" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/PARTNERSEQUITYOFTHEPARENTCOMPANYNarrativeDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#PARTNERSEQUITYOFTHEPARENTCOMPANYNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/PARTNERSEQUITYOFTHEPARENTCOMPANYNarrativeDetails" xlink:type="extended" id="i1f035ecc026144fb92037def93f4437a_PARTNERSEQUITYOFTHEPARENTCOMPANYNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_bdn_EarningsPerCommonPartnershipUnitLineItems_65ca2b33-818b-427a-8e18-bc528bf562f0" xlink:href="bdn-20230630.xsd#bdn_EarningsPerCommonPartnershipUnitLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_93fb358e-0d92-425d-8662-6ecff019a166" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_EarningsPerCommonPartnershipUnitLineItems_65ca2b33-818b-427a-8e18-bc528bf562f0" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_93fb358e-0d92-425d-8662-6ecff019a166" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareCashPaid_929e0916-cd5f-4b17-be99-3e32dfc2e9f1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockDividendsPerShareCashPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_EarningsPerCommonPartnershipUnitLineItems_65ca2b33-818b-427a-8e18-bc528bf562f0" xlink:to="loc_us-gaap_CommonStockDividendsPerShareCashPaid_929e0916-cd5f-4b17-be99-3e32dfc2e9f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStock_12820bfd-fc2f-4a32-8e6f-4502bca55910" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_EarningsPerCommonPartnershipUnitLineItems_65ca2b33-818b-427a-8e18-bc528bf562f0" xlink:to="loc_us-gaap_DividendsCommonStock_12820bfd-fc2f-4a32-8e6f-4502bca55910" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_RepurchaseProgramNumberOfMirrorUnitOfOperatingPartnershipRetiredForEachCommonShareRepurchased_693af9c2-95b8-4e27-9b1b-fe5456c08d35" xlink:href="bdn-20230630.xsd#bdn_RepurchaseProgramNumberOfMirrorUnitOfOperatingPartnershipRetiredForEachCommonShareRepurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_EarningsPerCommonPartnershipUnitLineItems_65ca2b33-818b-427a-8e18-bc528bf562f0" xlink:to="loc_bdn_RepurchaseProgramNumberOfMirrorUnitOfOperatingPartnershipRetiredForEachCommonShareRepurchased_693af9c2-95b8-4e27-9b1b-fe5456c08d35" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_f1a68f92-c75f-44cc-baaf-0385135d332a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_EarningsPerCommonPartnershipUnitLineItems_65ca2b33-818b-427a-8e18-bc528bf562f0" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_f1a68f92-c75f-44cc-baaf-0385135d332a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_EarningsPerCommonPartnershipUnitTable_c3ec02ef-81f4-4594-8abc-757066b1da48" xlink:href="bdn-20230630.xsd#bdn_EarningsPerCommonPartnershipUnitTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_bdn_EarningsPerCommonPartnershipUnitLineItems_65ca2b33-818b-427a-8e18-bc528bf562f0" xlink:to="loc_bdn_EarningsPerCommonPartnershipUnitTable_c3ec02ef-81f4-4594-8abc-757066b1da48" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_47765d2c-7915-4c88-8d65-b4a519de6ab4" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bdn_EarningsPerCommonPartnershipUnitTable_c3ec02ef-81f4-4594-8abc-757066b1da48" xlink:to="loc_srt_ConsolidatedEntitiesAxis_47765d2c-7915-4c88-8d65-b4a519de6ab4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_47765d2c-7915-4c88-8d65-b4a519de6ab4_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_47765d2c-7915-4c88-8d65-b4a519de6ab4" xlink:to="loc_srt_ConsolidatedEntitiesDomain_47765d2c-7915-4c88-8d65-b4a519de6ab4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_0ae72a33-54a5-4a63-87af-5632050162a4" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_47765d2c-7915-4c88-8d65-b4a519de6ab4" xlink:to="loc_srt_ConsolidatedEntitiesDomain_0ae72a33-54a5-4a63-87af-5632050162a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember_01c09780-6dd5-4a1e-a170-e9f07b80daed" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_0ae72a33-54a5-4a63-87af-5632050162a4" xlink:to="loc_srt_SubsidiariesMember_01c09780-6dd5-4a1e-a170-e9f07b80daed" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_3998766f-0046-4502-ac7a-13d73ccf98f3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bdn_EarningsPerCommonPartnershipUnitTable_c3ec02ef-81f4-4594-8abc-757066b1da48" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_3998766f-0046-4502-ac7a-13d73ccf98f3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_3998766f-0046-4502-ac7a-13d73ccf98f3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_3998766f-0046-4502-ac7a-13d73ccf98f3" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_3998766f-0046-4502-ac7a-13d73ccf98f3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_61eca53b-c7dd-4889-a899-b2b82e3bac30" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_3998766f-0046-4502-ac7a-13d73ccf98f3" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_61eca53b-c7dd-4889-a899-b2b82e3bac30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_baddef3a-3732-4210-9b41-7674a44c466a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_61eca53b-c7dd-4889-a899-b2b82e3bac30" xlink:to="loc_us-gaap_SubsequentEventMember_baddef3a-3732-4210-9b41-7674a44c466a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/SEGMENTINFORMATIONRealEstateInvestmentsatCostofCompanysReportableSegmentsDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#SEGMENTINFORMATIONRealEstateInvestmentsatCostofCompanysReportableSegmentsDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/SEGMENTINFORMATIONRealEstateInvestmentsatCostofCompanysReportableSegmentsDetails" xlink:type="extended" id="iac5dd712f0f04d16a1692a6c5e85ac91_SEGMENTINFORMATIONRealEstateInvestmentsatCostofCompanysReportableSegmentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_f1c614dd-e379-4d76-a06a-ed55e41d6e6a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyAtCost_f0a1a47a-7bcb-445e-aa35-78a088d148b4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateInvestmentPropertyAtCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_f1c614dd-e379-4d76-a06a-ed55e41d6e6a" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyAtCost_f0a1a47a-7bcb-445e-aa35-78a088d148b4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_6b7230dd-6d9e-4421-a69b-be7c6a2a8e57" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_f1c614dd-e379-4d76-a06a-ed55e41d6e6a" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_6b7230dd-6d9e-4421-a69b-be7c6a2a8e57" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopmentInProcess_f13f08be-ddba-4898-9ace-559516dc95cc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DevelopmentInProcess"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_f1c614dd-e379-4d76-a06a-ed55e41d6e6a" xlink:to="loc_us-gaap_DevelopmentInProcess_f13f08be-ddba-4898-9ace-559516dc95cc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandAvailableForDevelopment_63122c92-9f22-4915-bfd1-9d9575e15946" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LandAvailableForDevelopment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_f1c614dd-e379-4d76-a06a-ed55e41d6e6a" xlink:to="loc_us-gaap_LandAvailableForDevelopment_63122c92-9f22-4915-bfd1-9d9575e15946" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseCurrentAndNoncurrent_37811f63-9541-4fd5-a3e7-9d38b6f6d8d3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PrepaidExpenseCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_f1c614dd-e379-4d76-a06a-ed55e41d6e6a" xlink:to="loc_us-gaap_PrepaidExpenseCurrentAndNoncurrent_37811f63-9541-4fd5-a3e7-9d38b6f6d8d3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_82904abd-c3b4-4aff-bceb-fcb1dd8f0c19" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_f1c614dd-e379-4d76-a06a-ed55e41d6e6a" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_82904abd-c3b4-4aff-bceb-fcb1dd8f0c19" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_b6da1023-b10d-4b0b-8455-0f7ca8f2adc2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_82904abd-c3b4-4aff-bceb-fcb1dd8f0c19" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_b6da1023-b10d-4b0b-8455-0f7ca8f2adc2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_b6da1023-b10d-4b0b-8455-0f7ca8f2adc2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_b6da1023-b10d-4b0b-8455-0f7ca8f2adc2" xlink:to="loc_us-gaap_SegmentDomain_b6da1023-b10d-4b0b-8455-0f7ca8f2adc2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_f4a12d98-d586-4ddd-89af-614116e3d178" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_b6da1023-b10d-4b0b-8455-0f7ca8f2adc2" xlink:to="loc_us-gaap_SegmentDomain_f4a12d98-d586-4ddd-89af-614116e3d178" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_CoreSegmentTotalMember_604a2d13-ddf4-4701-827e-862c2bf0519b" xlink:href="bdn-20230630.xsd#bdn_CoreSegmentTotalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_f4a12d98-d586-4ddd-89af-614116e3d178" xlink:to="loc_bdn_CoreSegmentTotalMember_604a2d13-ddf4-4701-827e-862c2bf0519b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_PhiladelphiaCBDMember_2c8498d8-e81a-4968-b03e-97b01059d96b" xlink:href="bdn-20230630.xsd#bdn_PhiladelphiaCBDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_CoreSegmentTotalMember_604a2d13-ddf4-4701-827e-862c2bf0519b" xlink:to="loc_bdn_PhiladelphiaCBDMember_2c8498d8-e81a-4968-b03e-97b01059d96b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_PennsylvaniaSuburbsMember_e9925e10-0711-47a6-9555-5eda028de042" xlink:href="bdn-20230630.xsd#bdn_PennsylvaniaSuburbsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_CoreSegmentTotalMember_604a2d13-ddf4-4701-827e-862c2bf0519b" xlink:to="loc_bdn_PennsylvaniaSuburbsMember_e9925e10-0711-47a6-9555-5eda028de042" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_AustinTexasMember_3f39125d-e4eb-4cbc-ad15-9392b058479b" xlink:href="bdn-20230630.xsd#bdn_AustinTexasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bdn_CoreSegmentTotalMember_604a2d13-ddf4-4701-827e-862c2bf0519b" xlink:to="loc_bdn_AustinTexasMember_3f39125d-e4eb-4cbc-ad15-9392b058479b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_MetropolitanDCMember_56deb568-094b-4c8b-9725-4a5e3584ee17" xlink:href="bdn-20230630.xsd#bdn_MetropolitanDCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_f4a12d98-d586-4ddd-89af-614116e3d178" xlink:to="loc_bdn_MetropolitanDCMember_56deb568-094b-4c8b-9725-4a5e3584ee17" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOperatingActivitiesSegmentAxis_12f91bf9-e785-4175-bbee-a94c5eb28889" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOperatingActivitiesSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_82904abd-c3b4-4aff-bceb-fcb1dd8f0c19" xlink:to="loc_us-gaap_StatementOperatingActivitiesSegmentAxis_12f91bf9-e785-4175-bbee-a94c5eb28889" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentOperatingActivitiesDomain_12f91bf9-e785-4175-bbee-a94c5eb28889_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentOperatingActivitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementOperatingActivitiesSegmentAxis_12f91bf9-e785-4175-bbee-a94c5eb28889" xlink:to="loc_us-gaap_SegmentOperatingActivitiesDomain_12f91bf9-e785-4175-bbee-a94c5eb28889_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentOperatingActivitiesDomain_49bf3710-6498-4130-ba9d-18938b55b46e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentOperatingActivitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementOperatingActivitiesSegmentAxis_12f91bf9-e785-4175-bbee-a94c5eb28889" xlink:to="loc_us-gaap_SegmentOperatingActivitiesDomain_49bf3710-6498-4130-ba9d-18938b55b46e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDiscontinuedOperationsMember_e8790400-36b8-438d-9a68-5eb59aaad963" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentOperatingActivitiesDomain_49bf3710-6498-4130-ba9d-18938b55b46e" xlink:to="loc_us-gaap_SegmentDiscontinuedOperationsMember_e8790400-36b8-438d-9a68-5eb59aaad963" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentContinuingOperationsMember_8f0f03e1-efcb-4d3b-a92c-172b02a34293" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentContinuingOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentOperatingActivitiesDomain_49bf3710-6498-4130-ba9d-18938b55b46e" xlink:to="loc_us-gaap_SegmentContinuingOperationsMember_8f0f03e1-efcb-4d3b-a92c-172b02a34293" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/SEGMENTINFORMATIONNetOperatingIncomeofCompanysReportableSegmentsDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#SEGMENTINFORMATIONNetOperatingIncomeofCompanysReportableSegmentsDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/SEGMENTINFORMATIONNetOperatingIncomeofCompanysReportableSegmentsDetails" xlink:type="extended" id="i143e9938db184eb1931a7b7552fd461b_SEGMENTINFORMATIONNetOperatingIncomeofCompanysReportableSegmentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_7ebb94d0-2da3-4c01-bc13-a709c0b503ae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_049a3917-8cca-4d54-9e6c-1db5b6d78661" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_7ebb94d0-2da3-4c01-bc13-a709c0b503ae" xlink:to="loc_us-gaap_Revenues_049a3917-8cca-4d54-9e6c-1db5b6d78661" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_ab56c759-1fa3-4f04-b26f-6a0d46d295e1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_7ebb94d0-2da3-4c01-bc13-a709c0b503ae" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_ab56c759-1fa3-4f04-b26f-6a0d46d295e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_c4a5ae9c-c910-401e-920d-f130635b01b7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_7ebb94d0-2da3-4c01-bc13-a709c0b503ae" xlink:to="loc_us-gaap_GrossProfit_c4a5ae9c-c910-401e-920d-f130635b01b7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_80d79926-47f1-445b-8ca9-47d5f3472bc5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_7ebb94d0-2da3-4c01-bc13-a709c0b503ae" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_80d79926-47f1-445b-8ca9-47d5f3472bc5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_a6045aca-8198-4c0b-b807-b03badb7f0ed" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_80d79926-47f1-445b-8ca9-47d5f3472bc5" xlink:to="loc_srt_ConsolidationItemsAxis_a6045aca-8198-4c0b-b807-b03badb7f0ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_a6045aca-8198-4c0b-b807-b03badb7f0ed_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_a6045aca-8198-4c0b-b807-b03badb7f0ed" xlink:to="loc_srt_ConsolidationItemsDomain_a6045aca-8198-4c0b-b807-b03badb7f0ed_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_0f3ebe96-8182-47f5-b02a-b4f876c68797" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_a6045aca-8198-4c0b-b807-b03badb7f0ed" xlink:to="loc_srt_ConsolidationItemsDomain_0f3ebe96-8182-47f5-b02a-b4f876c68797" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_c64c8204-b535-4cc3-add8-96a6dcdba31c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_0f3ebe96-8182-47f5-b02a-b4f876c68797" xlink:to="loc_us-gaap_OperatingSegmentsMember_c64c8204-b535-4cc3-add8-96a6dcdba31c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_7e1c5141-d8d1-47c5-91d9-581eddaa0c15" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_0f3ebe96-8182-47f5-b02a-b4f876c68797" xlink:to="loc_us-gaap_CorporateNonSegmentMember_7e1c5141-d8d1-47c5-91d9-581eddaa0c15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_de5758b4-4f13-4bb9-a5a2-f2db6b3fdf25" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_80d79926-47f1-445b-8ca9-47d5f3472bc5" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_de5758b4-4f13-4bb9-a5a2-f2db6b3fdf25" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_de5758b4-4f13-4bb9-a5a2-f2db6b3fdf25_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_de5758b4-4f13-4bb9-a5a2-f2db6b3fdf25" xlink:to="loc_us-gaap_SegmentDomain_de5758b4-4f13-4bb9-a5a2-f2db6b3fdf25_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_effbe01c-ac02-4d0d-8c19-bcb26e64ebdd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_de5758b4-4f13-4bb9-a5a2-f2db6b3fdf25" xlink:to="loc_us-gaap_SegmentDomain_effbe01c-ac02-4d0d-8c19-bcb26e64ebdd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_PhiladelphiaCBDMember_0734262b-df75-43fc-a39b-e0b3118814df" xlink:href="bdn-20230630.xsd#bdn_PhiladelphiaCBDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_effbe01c-ac02-4d0d-8c19-bcb26e64ebdd" xlink:to="loc_bdn_PhiladelphiaCBDMember_0734262b-df75-43fc-a39b-e0b3118814df" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_PennsylvaniaSuburbsMember_e4ca3483-861b-4edc-b8f2-1d928f2016ae" xlink:href="bdn-20230630.xsd#bdn_PennsylvaniaSuburbsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_effbe01c-ac02-4d0d-8c19-bcb26e64ebdd" xlink:to="loc_bdn_PennsylvaniaSuburbsMember_e4ca3483-861b-4edc-b8f2-1d928f2016ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_AustinTexasMember_d9827817-bcfb-4aeb-b20b-2a3ba1dd2391" xlink:href="bdn-20230630.xsd#bdn_AustinTexasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_effbe01c-ac02-4d0d-8c19-bcb26e64ebdd" xlink:to="loc_bdn_AustinTexasMember_d9827817-bcfb-4aeb-b20b-2a3ba1dd2391" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_MetropolitanDCMember_b43e75e8-ee9b-4535-ba5c-0be2fd9b0167" xlink:href="bdn-20230630.xsd#bdn_MetropolitanDCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_effbe01c-ac02-4d0d-8c19-bcb26e64ebdd" xlink:to="loc_bdn_MetropolitanDCMember_b43e75e8-ee9b-4535-ba5c-0be2fd9b0167" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/SEGMENTINFORMATIONUnconsolidatedRealEstateVenturesofCompanysReportableSegmentsDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#SEGMENTINFORMATIONUnconsolidatedRealEstateVenturesofCompanysReportableSegmentsDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/SEGMENTINFORMATIONUnconsolidatedRealEstateVenturesofCompanysReportableSegmentsDetails" xlink:type="extended" id="i1199b74971e749d3b623448d651c94ff_SEGMENTINFORMATIONUnconsolidatedRealEstateVenturesofCompanysReportableSegmentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_c494081f-b793-4660-9dce-cee7866651ed" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentsJointVentures_053316e8-6719-44e1-9213-839e1d32e9e2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateInvestmentsJointVentures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c494081f-b793-4660-9dce-cee7866651ed" xlink:to="loc_us-gaap_RealEstateInvestmentsJointVentures_053316e8-6719-44e1-9213-839e1d32e9e2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_27c2534b-3973-4b88-8591-3fe5e28f51f8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c494081f-b793-4660-9dce-cee7866651ed" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_27c2534b-3973-4b88-8591-3fe5e28f51f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_808f2b04-b1d0-4ccf-9cf1-5b65b2ef2fc0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c494081f-b793-4660-9dce-cee7866651ed" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_808f2b04-b1d0-4ccf-9cf1-5b65b2ef2fc0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_242d608a-6d63-4c3a-878e-82c812bd26fd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_808f2b04-b1d0-4ccf-9cf1-5b65b2ef2fc0" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_242d608a-6d63-4c3a-878e-82c812bd26fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_242d608a-6d63-4c3a-878e-82c812bd26fd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_242d608a-6d63-4c3a-878e-82c812bd26fd" xlink:to="loc_us-gaap_SegmentDomain_242d608a-6d63-4c3a-878e-82c812bd26fd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_41e8dda3-975e-4cf5-bedb-0b55bd95ed0c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_242d608a-6d63-4c3a-878e-82c812bd26fd" xlink:to="loc_us-gaap_SegmentDomain_41e8dda3-975e-4cf5-bedb-0b55bd95ed0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_PhiladelphiaCBDMember_81eacaa0-b987-4116-968b-beb9d31626b2" xlink:href="bdn-20230630.xsd#bdn_PhiladelphiaCBDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_41e8dda3-975e-4cf5-bedb-0b55bd95ed0c" xlink:to="loc_bdn_PhiladelphiaCBDMember_81eacaa0-b987-4116-968b-beb9d31626b2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_MetropolitanDCMember_0e8b3ad8-6b7e-4494-807e-14642e9b957d" xlink:href="bdn-20230630.xsd#bdn_MetropolitanDCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_41e8dda3-975e-4cf5-bedb-0b55bd95ed0c" xlink:to="loc_bdn_MetropolitanDCMember_0e8b3ad8-6b7e-4494-807e-14642e9b957d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_MidAtlanticOfficeJointVentureMember_f4aaac90-af8b-413b-a7fb-acf9cea5cf30" xlink:href="bdn-20230630.xsd#bdn_MidAtlanticOfficeJointVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_41e8dda3-975e-4cf5-bedb-0b55bd95ed0c" xlink:to="loc_bdn_MidAtlanticOfficeJointVentureMember_f4aaac90-af8b-413b-a7fb-acf9cea5cf30" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_MAPVentureMember_99e357fd-f10d-422f-beed-081666a8b1d4" xlink:href="bdn-20230630.xsd#bdn_MAPVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_41e8dda3-975e-4cf5-bedb-0b55bd95ed0c" xlink:to="loc_bdn_MAPVentureMember_99e357fd-f10d-422f-beed-081666a8b1d4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_AustinTexasMember_f929fa05-825b-4d85-835d-053ab1ed6011" xlink:href="bdn-20230630.xsd#bdn_AustinTexasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_41e8dda3-975e-4cf5-bedb-0b55bd95ed0c" xlink:to="loc_bdn_AustinTexasMember_f929fa05-825b-4d85-835d-053ab1ed6011" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.brandywinerealty.com/role/COMMITMENTSANDCONTINGENCIESDetails" xlink:type="simple" xlink:href="bdn-20230630.xsd#COMMITMENTSANDCONTINGENCIESDetails"/>
  <link:definitionLink xlink:role="http://www.brandywinerealty.com/role/COMMITMENTSANDCONTINGENCIESDetails" xlink:type="extended" id="i38e1abe5db14483eb8d449e9f9325148_COMMITMENTSANDCONTINGENCIESDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_ee52cc33-e356-4c83-8061-605e0d698856" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_EquityMethodInvestmentSummarizedFinancialInformationDebt_485007ba-4fcf-4edc-bae0-723b98faa702" xlink:href="bdn-20230630.xsd#bdn_EquityMethodInvestmentSummarizedFinancialInformationDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_ee52cc33-e356-4c83-8061-605e0d698856" xlink:to="loc_bdn_EquityMethodInvestmentSummarizedFinancialInformationDebt_485007ba-4fcf-4edc-bae0-723b98faa702" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_LimitedPaymentGuaranteePercentOfPrincipleBalance_10538dbe-58a4-4866-912d-dffe87d84923" xlink:href="bdn-20230630.xsd#bdn_LimitedPaymentGuaranteePercentOfPrincipleBalance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_ee52cc33-e356-4c83-8061-605e0d698856" xlink:to="loc_bdn_LimitedPaymentGuaranteePercentOfPrincipleBalance_10538dbe-58a4-4866-912d-dffe87d84923" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_EquityMethodInvestmentAdditionalSummarizedFinancialInformationDebt_c237bff0-7899-4dc9-bfdc-07e8d1f703fc" xlink:href="bdn-20230630.xsd#bdn_EquityMethodInvestmentAdditionalSummarizedFinancialInformationDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_ee52cc33-e356-4c83-8061-605e0d698856" xlink:to="loc_bdn_EquityMethodInvestmentAdditionalSummarizedFinancialInformationDebt_c237bff0-7899-4dc9-bfdc-07e8d1f703fc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_CapitalCommitmentTargetsConstructionLoanAmount_aeb4df8e-7019-4292-9185-80195abad69f" xlink:href="bdn-20230630.xsd#bdn_CapitalCommitmentTargetsConstructionLoanAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_ee52cc33-e356-4c83-8061-605e0d698856" xlink:to="loc_bdn_CapitalCommitmentTargetsConstructionLoanAmount_aeb4df8e-7019-4292-9185-80195abad69f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentsJointVentures_46908e35-e070-4bb5-90b9-f8d0286afc0b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealEstateInvestmentsJointVentures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_ee52cc33-e356-4c83-8061-605e0d698856" xlink:to="loc_us-gaap_RealEstateInvestmentsJointVentures_46908e35-e070-4bb5-90b9-f8d0286afc0b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractualObligation_54bb7f41-1bcc-4b58-82d2-0fec86dc5a2d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractualObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_ee52cc33-e356-4c83-8061-605e0d698856" xlink:to="loc_us-gaap_ContractualObligation_54bb7f41-1bcc-4b58-82d2-0fec86dc5a2d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_EstimatedPotentialAdditionalContributionObligation_bfc2c807-ab65-40f8-b0df-06a81e9962cf" xlink:href="bdn-20230630.xsd#bdn_EstimatedPotentialAdditionalContributionObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_ee52cc33-e356-4c83-8061-605e0d698856" xlink:to="loc_bdn_EstimatedPotentialAdditionalContributionObligation_bfc2c807-ab65-40f8-b0df-06a81e9962cf" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_b2d69f8a-1768-470b-8eff-e5048d7ea08b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_ee52cc33-e356-4c83-8061-605e0d698856" xlink:to="loc_us-gaap_LossContingenciesTable_b2d69f8a-1768-470b-8eff-e5048d7ea08b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_71c22fcd-9340-400f-a61a-022ec7d9e439" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_b2d69f8a-1768-470b-8eff-e5048d7ea08b" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_71c22fcd-9340-400f-a61a-022ec7d9e439" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_71c22fcd-9340-400f-a61a-022ec7d9e439_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_71c22fcd-9340-400f-a61a-022ec7d9e439" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_71c22fcd-9340-400f-a61a-022ec7d9e439_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_5263db0d-d216-4ce3-969a-727221dcf776" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_71c22fcd-9340-400f-a61a-022ec7d9e439" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_5263db0d-d216-4ce3-969a-727221dcf776" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_UnconsolidatedRealEstateVenturesMember_7b258277-bd7e-4cf7-9f7e-f4fba858bb1e" xlink:href="bdn-20230630.xsd#bdn_UnconsolidatedRealEstateVenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_5263db0d-d216-4ce3-969a-727221dcf776" xlink:to="loc_bdn_UnconsolidatedRealEstateVenturesMember_7b258277-bd7e-4cf7-9f7e-f4fba858bb1e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_11298357-3839-4eb9-9bd3-3da889d1b406" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_b2d69f8a-1768-470b-8eff-e5048d7ea08b" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_11298357-3839-4eb9-9bd3-3da889d1b406" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_11298357-3839-4eb9-9bd3-3da889d1b406_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_11298357-3839-4eb9-9bd3-3da889d1b406" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_11298357-3839-4eb9-9bd3-3da889d1b406_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_f0e30538-8c0c-49fe-8a0f-26dbbfeded11" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_11298357-3839-4eb9-9bd3-3da889d1b406" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_f0e30538-8c0c-49fe-8a0f-26dbbfeded11" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_OneUptownVentureMember_f80620a3-6b2e-4a5a-93f8-f79e82626ee6" xlink:href="bdn-20230630.xsd#bdn_OneUptownVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_f0e30538-8c0c-49fe-8a0f-26dbbfeded11" xlink:to="loc_bdn_OneUptownVentureMember_f80620a3-6b2e-4a5a-93f8-f79e82626ee6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_A3025JFKBoulevardMember_7409f6fe-9e0c-489c-9d9d-a7b00a59b6de" xlink:href="bdn-20230630.xsd#bdn_A3025JFKBoulevardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_f0e30538-8c0c-49fe-8a0f-26dbbfeded11" xlink:to="loc_bdn_A3025JFKBoulevardMember_7409f6fe-9e0c-489c-9d9d-a7b00a59b6de" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_63110741-cb0f-4428-a27e-c0428d52a9d4" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_b2d69f8a-1768-470b-8eff-e5048d7ea08b" xlink:to="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_63110741-cb0f-4428-a27e-c0428d52a9d4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_63110741-cb0f-4428-a27e-c0428d52a9d4_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_63110741-cb0f-4428-a27e-c0428d52a9d4" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_63110741-cb0f-4428-a27e-c0428d52a9d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_df83b5ff-17d7-45da-bca4-75c9bc55f7a2" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_63110741-cb0f-4428-a27e-c0428d52a9d4" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_df83b5ff-17d7-45da-bca4-75c9bc55f7a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_A3151MarketStreetMember_879cef31-6a8d-4a75-938b-0c2cadc2c9a4" xlink:href="bdn-20230630.xsd#bdn_A3151MarketStreetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_df83b5ff-17d7-45da-bca4-75c9bc55f7a2" xlink:to="loc_bdn_A3151MarketStreetMember_879cef31-6a8d-4a75-938b-0c2cadc2c9a4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsByNatureAxis_9c492f21-e81e-42a0-b2f7-8074a2e6b7b5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GuaranteeObligationsByNatureAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_b2d69f8a-1768-470b-8eff-e5048d7ea08b" xlink:to="loc_us-gaap_GuaranteeObligationsByNatureAxis_9c492f21-e81e-42a0-b2f7-8074a2e6b7b5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_9c492f21-e81e-42a0-b2f7-8074a2e6b7b5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_9c492f21-e81e-42a0-b2f7-8074a2e6b7b5" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_9c492f21-e81e-42a0-b2f7-8074a2e6b7b5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_ad5779d6-6d43-419d-9b80-2d433b4e5ec1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_9c492f21-e81e-42a0-b2f7-8074a2e6b7b5" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_ad5779d6-6d43-419d-9b80-2d433b4e5ec1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_CarryGuaranteeMember_da95100b-31d9-4e30-b60f-e57db8053e8c" xlink:href="bdn-20230630.xsd#bdn_CarryGuaranteeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_ad5779d6-6d43-419d-9b80-2d433b4e5ec1" xlink:to="loc_bdn_CarryGuaranteeMember_da95100b-31d9-4e30-b60f-e57db8053e8c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentGuaranteeMember_e73e81fd-0e6b-40e1-809f-ba6e62b1095a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentGuaranteeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_ad5779d6-6d43-419d-9b80-2d433b4e5ec1" xlink:to="loc_us-gaap_PaymentGuaranteeMember_e73e81fd-0e6b-40e1-809f-ba6e62b1095a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_f2fcb8a6-6b4b-40cc-a687-e2c547ec1441" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_b2d69f8a-1768-470b-8eff-e5048d7ea08b" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_f2fcb8a6-6b4b-40cc-a687-e2c547ec1441" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f2fcb8a6-6b4b-40cc-a687-e2c547ec1441_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_f2fcb8a6-6b4b-40cc-a687-e2c547ec1441" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f2fcb8a6-6b4b-40cc-a687-e2c547ec1441_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ac09e778-28f1-46ee-9222-ad7e934fa725" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_f2fcb8a6-6b4b-40cc-a687-e2c547ec1441" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ac09e778-28f1-46ee-9222-ad7e934fa725" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bdn_DrexelSquareMember_ec3ee0bd-5f0f-459c-8fbf-c119e72eede8" xlink:href="bdn-20230630.xsd#bdn_DrexelSquareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ac09e778-28f1-46ee-9222-ad7e934fa725" xlink:to="loc_bdn_DrexelSquareMember_ec3ee0bd-5f0f-459c-8fbf-c119e72eede8" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
