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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2024 Workiva-->
<!--r:6c148191-6f67-4b18-be2c-389d145a7a90,g:7d9d9ffc-3be3-4a91-a1c9-a243cf853d6c-->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:seic="http://www.seic.com/20231231" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:dtr-types1="http://www.xbrl.org/dtr/type/2020-01-21" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2022-03-31" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.seic.com/20231231">
  <xs:import namespace="http://fasb.org/srt/2023" schemaLocation="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd"/>
  <xs:import namespace="http://fasb.org/us-gaap/2023" schemaLocation="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd"/>
  <xs:import namespace="http://www.w3.org/1999/xlink" schemaLocation="http://www.xbrl.org/2003/xlink-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/dtr/type/2020-01-21" schemaLocation="https://www.xbrl.org/dtr/type/2020-01-21/types.xsd"/>
  <xs:import namespace="http://www.xbrl.org/dtr/type/2022-03-31" schemaLocation="https://www.xbrl.org/dtr/type/2022-03-31/types.xsd"/>
  <xs:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/country/2023" schemaLocation="https://xbrl.sec.gov/country/2023/country-2023.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/dei/2023" schemaLocation="https://xbrl.sec.gov/dei/2023/dei-2023.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/ecd/2023" schemaLocation="https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd"/>
  <xs:annotation>
    <xs:appinfo>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="seic-20231231_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="seic-20231231_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="seic-20231231_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="seic-20231231_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:type="simple"/>
      <link:roleType id="Cover" roleURI="http://www.seic.com/role/Cover">
        <link:definition>0000001 - Document - Cover</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AuditInformation" roleURI="http://www.seic.com/role/AuditInformation">
        <link:definition>0000002 - Document - Audit Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedBalanceSheets" roleURI="http://www.seic.com/role/ConsolidatedBalanceSheets">
        <link:definition>0000003 - Statement - Consolidated Balance Sheets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedBalanceSheetsParenthetical" roleURI="http://www.seic.com/role/ConsolidatedBalanceSheetsParenthetical">
        <link:definition>0000004 - Statement - Consolidated Balance Sheets (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedStatementsofOperations" roleURI="http://www.seic.com/role/ConsolidatedStatementsofOperations">
        <link:definition>0000005 - Statement - Consolidated Statements of Operations</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedStatementsofComprehensiveIncome" roleURI="http://www.seic.com/role/ConsolidatedStatementsofComprehensiveIncome">
        <link:definition>0000006 - Statement - Consolidated Statements of Comprehensive Income</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedStatementsofComprehensiveIncomeParenthetical" roleURI="http://www.seic.com/role/ConsolidatedStatementsofComprehensiveIncomeParenthetical">
        <link:definition>0000007 - Statement - Consolidated Statements of Comprehensive Income (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedStatementsofChangesinEquity" roleURI="http://www.seic.com/role/ConsolidatedStatementsofChangesinEquity">
        <link:definition>0000008 - Statement - Consolidated Statements of Changes in Equity</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedStatementsofChangesinEquityParenthetical" roleURI="http://www.seic.com/role/ConsolidatedStatementsofChangesinEquityParenthetical">
        <link:definition>0000009 - Statement - Consolidated Statements of Changes in Equity (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedStatementsofCashFlows" roleURI="http://www.seic.com/role/ConsolidatedStatementsofCashFlows">
        <link:definition>0000010 - Statement - Consolidated Statements of Cash Flows</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SummaryofSignificantAccountingPolicies" roleURI="http://www.seic.com/role/SummaryofSignificantAccountingPolicies">
        <link:definition>0000011 - Disclosure - Summary of Significant Accounting Policies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="InvestmentinUnconsolidatedAffiliates" roleURI="http://www.seic.com/role/InvestmentinUnconsolidatedAffiliates">
        <link:definition>0000012 - Disclosure - Investment in Unconsolidated Affiliates</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CompositionofCertainFinancialStatementCaptions" roleURI="http://www.seic.com/role/CompositionofCertainFinancialStatementCaptions">
        <link:definition>0000013 - Disclosure - Composition of Certain Financial Statement Captions</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurements" roleURI="http://www.seic.com/role/FairValueMeasurements">
        <link:definition>0000014 - Disclosure - Fair Value Measurements</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="MarketableSecurities" roleURI="http://www.seic.com/role/MarketableSecurities">
        <link:definition>0000015 - Disclosure - Marketable Securities</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LineofCredit" roleURI="http://www.seic.com/role/LineofCredit">
        <link:definition>0000016 - Disclosure - Line of Credit</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ShareholdersEquity" roleURI="http://www.seic.com/role/ShareholdersEquity">
        <link:definition>0000017 - Disclosure - Shareholders' Equity</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AccumulatedOtherComprehensiveIncomeLoss" roleURI="http://www.seic.com/role/AccumulatedOtherComprehensiveIncomeLoss">
        <link:definition>0000018 - Disclosure - Accumulated Other Comprehensive Income (Loss)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlan" roleURI="http://www.seic.com/role/EmployeeBenefitPlan">
        <link:definition>0000019 - Disclosure - Employee Benefit Plan</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentsandContingencies" roleURI="http://www.seic.com/role/CommitmentsandContingencies">
        <link:definition>0000020 - Disclosure - Commitments and Contingencies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxes" roleURI="http://www.seic.com/role/IncomeTaxes">
        <link:definition>0000021 - Disclosure - Income Taxes</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessSegmentInformation" roleURI="http://www.seic.com/role/BusinessSegmentInformation">
        <link:definition>0000022 - Disclosure - Business Segment Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RelatedPartyTransactions" roleURI="http://www.seic.com/role/RelatedPartyTransactions">
        <link:definition>0000023 - Disclosure - Related Party Transactions</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="VoluntarySeparationProgram" roleURI="http://www.seic.com/role/VoluntarySeparationProgram">
        <link:definition>0000024 - Disclosure - Voluntary Separation Program</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessAcquisitions" roleURI="http://www.seic.com/role/BusinessAcquisitions">
        <link:definition>0000025 - Disclosure - Business Acquisitions</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssets" roleURI="http://www.seic.com/role/GoodwillandIntangibleAssets">
        <link:definition>0000026 - Disclosure - Goodwill and Intangible Assets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenuesfromContractswithCustomers" roleURI="http://www.seic.com/role/RevenuesfromContractswithCustomers">
        <link:definition>0000027 - Disclosure - Revenues from Contracts with Customers</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Leases" roleURI="http://www.seic.com/role/Leases">
        <link:definition>0000028 - Disclosure - Leases</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ScheduleIIValuationAndQualifyingAccountsAndReserves" roleURI="http://www.seic.com/role/ScheduleIIValuationAndQualifyingAccountsAndReserves">
        <link:definition>0000029 - Disclosure - Schedule II - Valuation And Qualifying Accounts And Reserves</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SummaryofSignificantAccountingPoliciesPolicies" roleURI="http://www.seic.com/role/SummaryofSignificantAccountingPoliciesPolicies">
        <link:definition>9954471 - Disclosure - Summary of Significant Accounting Policies (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SummaryofSignificantAccountingPoliciesTables" roleURI="http://www.seic.com/role/SummaryofSignificantAccountingPoliciesTables">
        <link:definition>9954472 - Disclosure - Summary of Significant Accounting Policies (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="InvestmentinUnconsolidatedAffiliatesTables" roleURI="http://www.seic.com/role/InvestmentinUnconsolidatedAffiliatesTables">
        <link:definition>9954473 - Disclosure - Investment in Unconsolidated Affiliates (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CompositionofCertainFinancialStatementCaptionsTables" roleURI="http://www.seic.com/role/CompositionofCertainFinancialStatementCaptionsTables">
        <link:definition>9954474 - Disclosure - Composition of Certain Financial Statement Captions (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurementsTables" roleURI="http://www.seic.com/role/FairValueMeasurementsTables">
        <link:definition>9954475 - Disclosure - Fair Value Measurements (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="MarketableSecuritiesTables" roleURI="http://www.seic.com/role/MarketableSecuritiesTables">
        <link:definition>9954476 - Disclosure - Marketable Securities (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ShareholdersEquityTables" roleURI="http://www.seic.com/role/ShareholdersEquityTables">
        <link:definition>9954477 - Disclosure - Shareholders' Equity (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AccumulatedOtherComprehensiveIncomeLossTables" roleURI="http://www.seic.com/role/AccumulatedOtherComprehensiveIncomeLossTables">
        <link:definition>9954478 - Disclosure - Accumulated Other Comprehensive Income (Loss) (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentsandContingenciesTables" roleURI="http://www.seic.com/role/CommitmentsandContingenciesTables">
        <link:definition>9954479 - Disclosure - Commitments and Contingencies (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesTables" roleURI="http://www.seic.com/role/IncomeTaxesTables">
        <link:definition>9954480 - Disclosure - Income Taxes (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessSegmentInformationTables" roleURI="http://www.seic.com/role/BusinessSegmentInformationTables">
        <link:definition>9954481 - Disclosure - Business Segment Information (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessAcquisitionsTables" roleURI="http://www.seic.com/role/BusinessAcquisitionsTables">
        <link:definition>9954482 - Disclosure - Business Acquisitions (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsTables" roleURI="http://www.seic.com/role/GoodwillandIntangibleAssetsTables">
        <link:definition>9954483 - Disclosure - Goodwill and Intangible Assets (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenuesfromContractswithCustomersTables" roleURI="http://www.seic.com/role/RevenuesfromContractswithCustomersTables">
        <link:definition>9954484 - Disclosure - Revenues from Contracts with Customers (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesTables" roleURI="http://www.seic.com/role/LeasesTables">
        <link:definition>9954485 - Disclosure - Leases (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SummaryofSignificantAccountingPoliciesNarrativeDetails" roleURI="http://www.seic.com/role/SummaryofSignificantAccountingPoliciesNarrativeDetails">
        <link:definition>9954486 - Disclosure - Summary of Significant Accounting Policies (Narrative) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SummaryofSignificantAccountingPoliciesExpectedAmortizationExpensesDetails" roleURI="http://www.seic.com/role/SummaryofSignificantAccountingPoliciesExpectedAmortizationExpensesDetails">
        <link:definition>9954487 - Disclosure - Summary of Significant Accounting Policies (Expected Amortization Expenses) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SummaryofSignificantAccountingPoliciesCalculationOfBasicAndDilutedEarningsPerShareDetails" roleURI="http://www.seic.com/role/SummaryofSignificantAccountingPoliciesCalculationOfBasicAndDilutedEarningsPerShareDetails">
        <link:definition>9954488 - Disclosure - Summary of Significant Accounting Policies (Calculation Of Basic And Diluted Earnings Per Share) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="InvestmentinUnconsolidatedAffiliatesNarrativeDetails" roleURI="http://www.seic.com/role/InvestmentinUnconsolidatedAffiliatesNarrativeDetails">
        <link:definition>9954489 - Disclosure - Investment in Unconsolidated Affiliates (Narrative) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="InvestmentinUnconsolidatedAffiliatesCondensedStatementsofOperationsofLSVDetails" roleURI="http://www.seic.com/role/InvestmentinUnconsolidatedAffiliatesCondensedStatementsofOperationsofLSVDetails">
        <link:definition>9954490 - Disclosure - Investment in Unconsolidated Affiliates (Condensed Statements of Operations of LSV) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="InvestmentinUnconsolidatedAffiliatesCondensedBalanceSheetsofLSVDetails" roleURI="http://www.seic.com/role/InvestmentinUnconsolidatedAffiliatesCondensedBalanceSheetsofLSVDetails">
        <link:definition>9954491 - Disclosure - Investment in Unconsolidated Affiliates (Condensed Balance Sheets of LSV) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CompositionofCertainFinancialStatementCaptionsReceivablesDetails" roleURI="http://www.seic.com/role/CompositionofCertainFinancialStatementCaptionsReceivablesDetails">
        <link:definition>9954492 - Disclosure - Composition of Certain Financial Statement Captions (Receivables) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CompositionofCertainFinancialStatementCaptionsPropertyAndEquipmentDetails" roleURI="http://www.seic.com/role/CompositionofCertainFinancialStatementCaptionsPropertyAndEquipmentDetails">
        <link:definition>9954493 - Disclosure - Composition of Certain Financial Statement Captions (Property And Equipment) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CompositionofCertainFinancialStatementCaptionsCompositionofCertainFinancialStatementCaptionsDeferredContractCostsDetails" roleURI="http://www.seic.com/role/CompositionofCertainFinancialStatementCaptionsCompositionofCertainFinancialStatementCaptionsDeferredContractCostsDetails">
        <link:definition>9954494 - Disclosure - Composition of Certain Financial Statement Captions Composition of Certain Financial Statement Captions (Deferred Contract Costs) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CompositionofCertainFinancialStatementCaptionsOtherAssetsDetails" roleURI="http://www.seic.com/role/CompositionofCertainFinancialStatementCaptionsOtherAssetsDetails">
        <link:definition>9954495 - Disclosure - Composition of Certain Financial Statement Captions (Other Assets) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CompositionofCertainFinancialStatementCaptionsAccruedLiabilitiesDetails" roleURI="http://www.seic.com/role/CompositionofCertainFinancialStatementCaptionsAccruedLiabilitiesDetails">
        <link:definition>9954496 - Disclosure - Composition of Certain Financial Statement Captions (Accrued Liabilities) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurementsDetails" roleURI="http://www.seic.com/role/FairValueMeasurementsDetails">
        <link:definition>9954497 - Disclosure - Fair Value Measurements (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="MarketableSecuritiesNarrativeDetails" roleURI="http://www.seic.com/role/MarketableSecuritiesNarrativeDetails">
        <link:definition>9954498 - Disclosure - Marketable Securities (Narrative) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="MarketableSecuritiesInvestmentsAvailableForSaleDetails" roleURI="http://www.seic.com/role/MarketableSecuritiesInvestmentsAvailableForSaleDetails">
        <link:definition>9954499 - Disclosure - Marketable Securities (Investments Available For Sale) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="MarketableSecuritiesInvestmentsAvailableForSaleDetails_1" roleURI="http://www.seic.com/role/MarketableSecuritiesInvestmentsAvailableForSaleDetails_1">
        <link:definition>9954499 - Disclosure - Marketable Securities (Investments Available For Sale) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="MarketableSecuritiesScheduleofAvailableforSaleDebtSecuritiesbyMaturityDetails" roleURI="http://www.seic.com/role/MarketableSecuritiesScheduleofAvailableforSaleDebtSecuritiesbyMaturityDetails">
        <link:definition>9954500 - Disclosure - Marketable Securities - Schedule of Available-for-Sale Debt Securities by Maturity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LineofCreditDetails" roleURI="http://www.seic.com/role/LineofCreditDetails">
        <link:definition>9954501 - Disclosure - Line of Credit (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ShareholdersEquityStockBasedCompensationExpenseDetails" roleURI="http://www.seic.com/role/ShareholdersEquityStockBasedCompensationExpenseDetails">
        <link:definition>9954502 - Disclosure - Shareholders' Equity (Stock-Based Compensation Expense) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ShareholdersEquityNarrativeDetails" roleURI="http://www.seic.com/role/ShareholdersEquityNarrativeDetails">
        <link:definition>9954503 - Disclosure - Shareholders' Equity (Narrative) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ShareholdersEquityAssumptionsUsedInTheWeightedAverageFairValueOfStockOptionsGrantedDetails" roleURI="http://www.seic.com/role/ShareholdersEquityAssumptionsUsedInTheWeightedAverageFairValueOfStockOptionsGrantedDetails">
        <link:definition>9954504 - Disclosure - Shareholders' Equity (Assumptions Used In The Weighted Average Fair Value Of Stock Options Granted) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ShareholdersEquityRSUActivityDetails" roleURI="http://www.seic.com/role/ShareholdersEquityRSUActivityDetails">
        <link:definition>9954505 - Disclosure - Shareholders' Equity (RSU Activity) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ShareholdersEquityStockOptionPlansDetails" roleURI="http://www.seic.com/role/ShareholdersEquityStockOptionPlansDetails">
        <link:definition>9954506 - Disclosure - Shareholders' Equity (Stock Option Plans) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ShareholdersEquityCommonStockBuybackDetails" roleURI="http://www.seic.com/role/ShareholdersEquityCommonStockBuybackDetails">
        <link:definition>9954507 - Disclosure - Shareholders' Equity (Common Stock Buyback) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AccumulatedOtherComprehensiveIncomeLossNetofTaxDetails" roleURI="http://www.seic.com/role/AccumulatedOtherComprehensiveIncomeLossNetofTaxDetails">
        <link:definition>9954508 - Disclosure - Accumulated Other Comprehensive Income (Loss), Net of Tax (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlanDetails" roleURI="http://www.seic.com/role/EmployeeBenefitPlanDetails">
        <link:definition>9954509 - Disclosure - Employee Benefit Plan (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentsandContingenciesNarrativeDetails" roleURI="http://www.seic.com/role/CommitmentsandContingenciesNarrativeDetails">
        <link:definition>9954510 - Disclosure - Commitments and Contingencies (Narrative) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentsandContingenciesScheduleOfNoncancellableMinimumCommitmentsDetails" roleURI="http://www.seic.com/role/CommitmentsandContingenciesScheduleOfNoncancellableMinimumCommitmentsDetails">
        <link:definition>9954511 - Disclosure - Commitments and Contingencies (Schedule Of Noncancellable Minimum Commitments) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesScheduleofFederalandStateandForeignIncomeTaxProvisionDetails" roleURI="http://www.seic.com/role/IncomeTaxesScheduleofFederalandStateandForeignIncomeTaxProvisionDetails">
        <link:definition>9954512 - Disclosure - Income Taxes (Schedule of Federal and State and Foreign Income Tax Provision) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesComponentsofNetIncomeBeforeIncomeTaxesDetails" roleURI="http://www.seic.com/role/IncomeTaxesComponentsofNetIncomeBeforeIncomeTaxesDetails">
        <link:definition>9954513 - Disclosure - Income Taxes (Components of Net Income Before Income Taxes) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesEffectiveIncomeTaxRateReconciliationatFederalStatutoryIncomeTaxRateDetails" roleURI="http://www.seic.com/role/IncomeTaxesEffectiveIncomeTaxRateReconciliationatFederalStatutoryIncomeTaxRateDetails">
        <link:definition>9954514 - Disclosure - Income Taxes (Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesScheduleofDeferredTaxAssetsandLiabilitiesDetails" roleURI="http://www.seic.com/role/IncomeTaxesScheduleofDeferredTaxAssetsandLiabilitiesDetails">
        <link:definition>9954515 - Disclosure - Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesNarrativeDetails" roleURI="http://www.seic.com/role/IncomeTaxesNarrativeDetails">
        <link:definition>9954516 - Disclosure - Income Taxes (Narrative) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesUnrecognizedTaxBenefitDetails" roleURI="http://www.seic.com/role/IncomeTaxesUnrecognizedTaxBenefitDetails">
        <link:definition>9954517 - Disclosure - Income Taxes (Unrecognized Tax Benefit) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessSegmentInformationScheduleofFinancialInformationaboutBusinessSegmentsDetails" roleURI="http://www.seic.com/role/BusinessSegmentInformationScheduleofFinancialInformationaboutBusinessSegmentsDetails">
        <link:definition>9954518 - Disclosure - Business Segment Information (Schedule of Financial Information about Business Segments) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessSegmentInformationReconciliationofTotalOperatingProfitReportedforBusinessSegmentstoIncomefromOperationsinConsolidatedStatementsofOperationsDetails" roleURI="http://www.seic.com/role/BusinessSegmentInformationReconciliationofTotalOperatingProfitReportedforBusinessSegmentstoIncomefromOperationsinConsolidatedStatementsofOperationsDetails">
        <link:definition>9954519 - Disclosure - Business Segment Information (Reconciliation of Total Operating Profit Reported for Business Segments to Income from Operations in Consolidated Statements of Operations) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessSegmentInformationScheduleOfAdditionalInformationPertainingToBusinessSegmentsDetails" roleURI="http://www.seic.com/role/BusinessSegmentInformationScheduleOfAdditionalInformationPertainingToBusinessSegmentsDetails">
        <link:definition>9954520 - Disclosure - Business Segment Information (Schedule Of Additional Information Pertaining To Business Segments) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessSegmentInformationScheduleofRevenuesAndAssetsBasedOnLocationDetails" roleURI="http://www.seic.com/role/BusinessSegmentInformationScheduleofRevenuesAndAssetsBasedOnLocationDetails">
        <link:definition>9954521 - Disclosure - Business Segment Information (Schedule of Revenues And Assets Based On Location) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RelatedPartyTransactionsDetails" roleURI="http://www.seic.com/role/RelatedPartyTransactionsDetails">
        <link:definition>9954522 - Disclosure - Related Party Transactions (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="VoluntarySeparationProgramDetails" roleURI="http://www.seic.com/role/VoluntarySeparationProgramDetails">
        <link:definition>9954523 - Disclosure - Voluntary Separation Program (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessAcquisitionsAdditionalInformationDetails" roleURI="http://www.seic.com/role/BusinessAcquisitionsAdditionalInformationDetails">
        <link:definition>9954524 - Disclosure - Business Acquisitions (Additional Information) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessAcquisitionsPurchasePriceAllocationDetails" roleURI="http://www.seic.com/role/BusinessAcquisitionsPurchasePriceAllocationDetails">
        <link:definition>9954525 - Disclosure - Business Acquisitions (Purchase Price Allocation) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsScheduleofGoodwillDetails" roleURI="http://www.seic.com/role/GoodwillandIntangibleAssetsScheduleofGoodwillDetails">
        <link:definition>9954526 - Disclosure - Goodwill and Intangible Assets (Schedule of Goodwill) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsScheduleofIntangibleAssetsDetails" roleURI="http://www.seic.com/role/GoodwillandIntangibleAssetsScheduleofIntangibleAssetsDetails">
        <link:definition>9954527 - Disclosure - Goodwill and Intangible Assets (Schedule of Intangible Assets) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsNarrativeDetails" roleURI="http://www.seic.com/role/GoodwillandIntangibleAssetsNarrativeDetails">
        <link:definition>9954528 - Disclosure - Goodwill and Intangible Assets (Narrative) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsFutureAmortizationExpensesDetails" roleURI="http://www.seic.com/role/GoodwillandIntangibleAssetsFutureAmortizationExpensesDetails">
        <link:definition>9954529 - Disclosure - Goodwill and Intangible Assets (Future Amortization Expenses) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenuesfromContractswithCustomersDetails" roleURI="http://www.seic.com/role/RevenuesfromContractswithCustomersDetails">
        <link:definition>9954530 - Disclosure - Revenues from Contracts with Customers (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesNarrativeDetails" roleURI="http://www.seic.com/role/LeasesNarrativeDetails">
        <link:definition>9954531 - Disclosure - Leases (Narrative) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesScheduleofFutureMinimumLeasePaymentsDetails" roleURI="http://www.seic.com/role/LeasesScheduleofFutureMinimumLeasePaymentsDetails">
        <link:definition>9954532 - Disclosure - Leases (Schedule of Future Minimum Lease Payments) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesScheduleofFutureMinimumLeasePaymentsDetails_1" roleURI="http://www.seic.com/role/LeasesScheduleofFutureMinimumLeasePaymentsDetails_1">
        <link:definition>9954532 - Disclosure - Leases (Schedule of Future Minimum Lease Payments) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesSupplementalConsolidatedBalanceSheetInformationRelatedtoOperatingLeasesDetails" roleURI="http://www.seic.com/role/LeasesSupplementalConsolidatedBalanceSheetInformationRelatedtoOperatingLeasesDetails">
        <link:definition>9954533 - Disclosure - Leases (Supplemental Consolidated Balance Sheet Information Related to Operating Leases) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesSupplementalCashFlowInformationRelatedtoOperatingLeasesDetails" roleURI="http://www.seic.com/role/LeasesSupplementalCashFlowInformationRelatedtoOperatingLeasesDetails">
        <link:definition>9954534 - Disclosure - Leases (Supplemental Cash Flow Information Related to Operating Leases) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ScheduleIIValuationandQualifyingAccountsandReservesDetails" roleURI="http://www.seic.com/role/ScheduleIIValuationandQualifyingAccountsandReservesDetails">
        <link:definition>9954535 - Disclosure - Schedule II - Valuation and Qualifying Accounts and Reserves (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
    </xs:appinfo>
  </xs:annotation>
  <xs:element id="seic_LesseeOperatingLeaseLiabilityToBePaidDueYearFiveAndThereafter" abstract="false" name="LesseeOperatingLeaseLiabilityToBePaidDueYearFiveAndThereafter" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_UnrecognizedTaxBenefitIncludingInterestAndPenalties" abstract="false" name="UnrecognizedTaxBenefitIncludingInterestAndPenalties" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_EquitySecuritiesFVNIAccumulatedGrossUnrealizedGainBeforeTax" abstract="false" name="EquitySecuritiesFVNIAccumulatedGrossUnrealizedGainBeforeTax" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_PrivateBankMember" abstract="true" name="PrivateBankMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_AccountFeesAndOtherMember" abstract="true" name="AccountFeesAndOtherMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_DeferredTaxAssetsTaxCreditCarryforwardsAndOperatingLossCarryforwards" abstract="false" name="DeferredTaxAssetsTaxCreditCarryforwardsAndOperatingLossCarryforwards" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsNetOfCurrentLiabilities" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsNetOfCurrentLiabilities" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_CapitalizedContractCostsNetOfAmortization" abstract="false" name="CapitalizedContractCostsNetOfAmortization" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_CapitalizedComputerSoftwareExpectedAmortizationYearOne" abstract="false" name="CapitalizedComputerSoftwareExpectedAmortizationYearOne" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_AltigoMember" abstract="true" name="AltigoMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="seic_SeiWealthPlatformMember" abstract="true" name="SeiWealthPlatformMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_OperatingLeaseRentExpenses" abstract="false" name="OperatingLeaseRentExpenses" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_CommissionsEarnedFromRelatedPartyMember" abstract="true" name="CommissionsEarnedFromRelatedPartyMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="seic_XPSPensionsNexusLimitedMember" abstract="true" name="XPSPensionsNexusLimitedMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="seic_CapitalizedSoftwareDevelopmentCostsInProgress" abstract="false" name="CapitalizedSoftwareDevelopmentCostsInProgress" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_InvestmentOperationsFeesMember" abstract="true" name="InvestmentOperationsFeesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_UnrecognizedTaxBenefitsTaxPositionsRelatedToCurrentYearAbstract" abstract="true" name="UnrecognizedTaxBenefitsTaxPositionsRelatedToCurrentYearAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="seic_AccruedSubAdvisoryDistributionAndOtherAssetManagementFeesCurrent" abstract="false" name="AccruedSubAdvisoryDistributionAndOtherAssetManagementFeesCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_ShareBasedPaymentArrangementExpenseVoluntarySeparationProgramAdjustmentToPreviouslyRecognizedAmount" abstract="false" name="ShareBasedPaymentArrangementExpenseVoluntarySeparationProgramAdjustmentToPreviouslyRecognizedAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_OtherGeographicAreasMember" abstract="true" name="OtherGeographicAreasMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_LesseeOperatingLeaseLeaseNotYetCommencedLiability" abstract="false" name="LesseeOperatingLeaseLeaseNotYetCommencedLiability" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_PlanModificationDomain" abstract="true" name="PlanModificationDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_SoftwareFacilitiesAndEquipmentLeasesMember" abstract="true" name="SoftwareFacilitiesAndEquipmentLeasesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_SoftwareRoyaltiesAndOtherInformationProcessingCosts" abstract="false" name="SoftwareRoyaltiesAndOtherInformationProcessingCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_DebtSecuritiesAvailableForSaleAndEquitySecuritiesFVNICost" abstract="false" name="DebtSecuritiesAvailableForSaleAndEquitySecuritiesFVNICost" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_DebtSecuritiesAvailableForSaleAndEquitySecuritiesFVNIAccumulatedGrossUnrealizedLossBeforeTax" abstract="false" name="DebtSecuritiesAvailableForSaleAndEquitySecuritiesFVNIAccumulatedGrossUnrealizedLossBeforeTax" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_ProfessionalServicesFeesMember" abstract="true" name="ProfessionalServicesFeesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_InvestmentsInNewBusinessesMember" abstract="true" name="InvestmentsInNewBusinessesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_UnrecognizedTaxBenefitsTaxPositionsRelatedToPriorYearsAbstract" abstract="true" name="UnrecognizedTaxBenefitsTaxPositionsRelatedToPriorYearsAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="seic_EffectiveIncomeTaxRateReconciliationTaxBenefitFromStockOptionExercisesPercent" abstract="false" name="EffectiveIncomeTaxRateReconciliationTaxBenefitFromStockOptionExercisesPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="seic_EquitySecuritiesFVNIAccumulatedGrossUnrealizedLossBeforeTax" abstract="false" name="EquitySecuritiesFVNIAccumulatedGrossUnrealizedLossBeforeTax" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_EmployeeStockPurchasePlanMember" abstract="true" name="EmployeeStockPurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_LineOfCreditFacilityConditionalIncreaseDecreaseNet" abstract="false" name="LineOfCreditFacilityConditionalIncreaseDecreaseNet" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_NovusPartnersMember" abstract="true" name="NovusPartnersMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_DebtSecuritiesAvailableForSaleAndEquitySecuritiesFVNIAccumulatedGrossUnrealizedGainBeforeTax" abstract="false" name="DebtSecuritiesAvailableForSaleAndEquitySecuritiesFVNIAccumulatedGrossUnrealizedGainBeforeTax" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_InstitutionalInvestorsMember" abstract="true" name="InstitutionalInvestorsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_CapitalizedContractCostAmountCapitalizedDuringPeriod" abstract="false" name="CapitalizedContractCostAmountCapitalizedDuringPeriod" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_LesseeOperatingLeaseLeaseArrangementDomain" abstract="true" name="LesseeOperatingLeaseLeaseArrangementDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_CapitalizedComputerSoftwareExpectedAmortizationYearThree" abstract="false" name="CapitalizedComputerSoftwareExpectedAmortizationYearThree" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_CommonStockBuybackMember" abstract="true" name="CommonStockBuybackMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_LesseeOperatingLeaseLeaseArrangementAxis" abstract="true" name="LesseeOperatingLeaseLeaseArrangementAxis" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType"/>
  <xs:element id="seic_DeferredTaxLiabilitiesDeferredExpenseCapitalizedContractCost" abstract="false" name="DeferredTaxLiabilitiesDeferredExpenseCapitalizedContractCost" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_ShareBasedCompensationArrangementByShareBasedPaymentAwardMarketPaidPriceOfferingDate" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardMarketPaidPriceOfferingDate" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="seic_SettlementandLapseofStatuteMember" abstract="true" name="SettlementandLapseofStatuteMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_LineOfCreditFacilityFrontingFeePercentage" abstract="false" name="LineOfCreditFacilityFrontingFeePercentage" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="seic_ProfessionalServicesFeesOneTimeEarlyTerminationFeesMember" abstract="true" name="ProfessionalServicesFeesOneTimeEarlyTerminationFeesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_AssetsAndLiabilitiesLesseeTableTextBlock" abstract="false" name="AssetsAndLiabilitiesLesseeTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:textBlockItemType"/>
  <xs:element id="seic_BusinessCombinationContingentConsiderationLiabilityPeriodOfRecognition" abstract="false" name="BusinessCombinationContingentConsiderationLiabilityPeriodOfRecognition" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="seic_SubadvisoryDistributionAndOtherAssetManagementCosts" abstract="false" name="SubadvisoryDistributionAndOtherAssetManagementCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_PlanModificationAxis" abstract="true" name="PlanModificationAxis" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType"/>
  <xs:element id="seic_EquitiesAndOtherMutualFundsMember" abstract="true" name="EquitiesAndOtherMutualFundsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_UnrecognizedTaxBenefitsRelatedToLapseofStatuteOfLimitationsPreviouslyUnrecognized" abstract="false" name="UnrecognizedTaxBenefitsRelatedToLapseofStatuteOfLimitationsPreviouslyUnrecognized" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_LSVAssetManagementMember" abstract="true" name="LSVAssetManagementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_DebtSecuritiesAvailableForSaleAndEquitySecuritiesFVNI" abstract="false" name="DebtSecuritiesAvailableForSaleAndEquitySecuritiesFVNI" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_ReceivablesGrossCurrent" abstract="false" name="ReceivablesGrossCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_ShareBasedPaymentArrangementExpenseIncreaseDecrease" abstract="false" name="ShareBasedPaymentArrangementExpenseIncreaseDecrease" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_InvestmentProcessingFeesSaaSMember" abstract="true" name="InvestmentProcessingFeesSaaSMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_InformationProcessingAndSoftwareServicingFeesMember" abstract="true" name="InformationProcessingAndSoftwareServicingFeesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_SeiInvestmentsDistributionCoSidcoMember" abstract="true" name="SeiInvestmentsDistributionCoSidcoMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_InvestmentManagersMember" abstract="true" name="InvestmentManagersMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_TaxCreditCarryforwardsAndOperatingLossCarryforwardsValuationAllowance" abstract="false" name="TaxCreditCarryforwardsAndOperatingLossCarryforwardsValuationAllowance" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_DeferredTaxAssetCapitalizedResearchAndDevelopmentCosts" abstract="false" name="DeferredTaxAssetCapitalizedResearchAndDevelopmentCosts" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_VoluntarySeparationProgramMember" abstract="true" name="VoluntarySeparationProgramMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_SEISponsoredMutualFundsMember" abstract="true" name="SEISponsoredMutualFundsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_A2021CreditFacilityMember" abstract="true" name="A2021CreditFacilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_CapitalizedComputerSoftwareExpectedAmortizationYearFour" abstract="false" name="CapitalizedComputerSoftwareExpectedAmortizationYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_TwoThousandFourteenPlanMember" abstract="true" name="TwoThousandFourteenPlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_SeiInvestmentsEuropeLimitedMember" abstract="true" name="SeiInvestmentsEuropeLimitedMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_CapitalizedContractCostAcceleratedAmortization" abstract="false" name="CapitalizedContractCostAcceleratedAmortization" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_SummaryofSignificantAccountingPoliciesLineItems" abstract="true" name="SummaryofSignificantAccountingPoliciesLineItems" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="seic_AccruedVoluntarySeparationProgramCurrent" abstract="false" name="AccruedVoluntarySeparationProgramCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_SummaryOfSignificantAccountingPoliciesTable" abstract="true" name="SummaryOfSignificantAccountingPoliciesTable" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType"/>
  <xs:element id="seic_CapitalizedComputerSoftwareExpectedAmortizationYearTwo" abstract="false" name="CapitalizedComputerSoftwareExpectedAmortizationYearTwo" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_DebtInstrumentInterestRatesAccrualNumberOfPrecedingFiscalQuarters" abstract="false" name="DebtInstrumentInterestRatesAccrualNumberOfPrecedingFiscalQuarters" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="seic_InvestmentProcessingFeesPaaSMember" abstract="true" name="InvestmentProcessingFeesPaaSMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_ResearchAndDevelopmentTaxCreditCarryforwardMember" abstract="true" name="ResearchAndDevelopmentTaxCreditCarryforwardMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_HuntingtonSteeleLLCMember" abstract="true" name="HuntingtonSteeleLLCMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_PurchasedSoftwareMember" abstract="true" name="PurchasedSoftwareMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_InvestmentManagementFeesFromInvestmentManagementAgreementsMember" abstract="true" name="InvestmentManagementFeesFromInvestmentManagementAgreementsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_FeesEarnedFromRelatedPartyMember" abstract="true" name="FeesEarnedFromRelatedPartyMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="seic_SeiSponsoredOpenEndedMoneyMarketMutualFundsMember" abstract="true" name="SeiSponsoredOpenEndedMoneyMarketMutualFundsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_LIBORMember" abstract="true" name="LIBORMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="seic_InvestmentManagementFeesFromInvestmentProductsMember" abstract="true" name="InvestmentManagementFeesFromInvestmentProductsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_CompensationBenefitsAndOtherPersonnel" abstract="false" name="CompensationBenefitsAndOtherPersonnel" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardWaitingPeriod" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardWaitingPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="seic_InvestmentAdvisorsMember" abstract="true" name="InvestmentAdvisorsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_InvestmentFundsSponsoredByLSVMember" abstract="true" name="InvestmentFundsSponsoredByLSVMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_AccumulatedOtherComprehensiveIncomeLossDebtSecuritiesAvailableForSaleSecuritiesAdjustmentTax" abstract="false" name="AccumulatedOtherComprehensiveIncomeLossDebtSecuritiesAvailableForSaleSecuritiesAdjustmentTax" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_CapitalizedComputerSoftwareExpectedAmortizationYearFive" abstract="false" name="CapitalizedComputerSoftwareExpectedAmortizationYearFive" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="seic_AssetManagementAdministrationAndDistributionFeesMember" abstract="true" name="AssetManagementAdministrationAndDistributionFeesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="seic_AuditInformationAbstract" abstract="true" name="AuditInformationAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
</xs:schema>
