<?xml version="1.0" encoding="us-ascii"?>
<!-- DFS ActiveDisclosure(SM) XBRL Schema Document - http://www.dfsco.com/financial-services/ -->
<!-- Creation Date      : 2018-05-09T19:42:31.2083734+00:00 -->
<!-- Version            : 2.9.6605.1333 -->
<!-- Package ID         : b934e5ecd38940d79e4236ef4b199cfa -->
<!-- Copyright (c) 2018 Donnelley Financial, LLC. All Rights Reserved. -->
<schema xmlns:nonnum="http://www.xbrl.org/dtr/type/non-numeric" xmlns:num="http://www.xbrl.org/dtr/type/numeric" xmlns:us-types="http://fasb.org/us-types/2017-01-31" xmlns:stpr="http://xbrl.sec.gov/stpr/2011-01-31" xmlns:naics="http://xbrl.sec.gov/naics/2017-01-31" xmlns:invest="http://xbrl.sec.gov/invest/2013-01-31" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:us-gaap="http://fasb.org/us-gaap/2017-01-31" xmlns:dei="http://xbrl.sec.gov/dei/2014-01-31" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:country="http://xbrl.sec.gov/country/2017-01-31" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:currency="http://xbrl.sec.gov/currency/2017-01-31" xmlns:adtn="http://www.adtran.com/20180331" xmlns:exch="http://xbrl.sec.gov/exch/2017-01-31" xmlns:sic="http://xbrl.sec.gov/sic/2011-01-31" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.adtran.com/20180331" xmlns="http://www.w3.org/2001/XMLSchema">
  <import schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" namespace="http://www.xbrl.org/2003/instance" />
  <import schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" namespace="http://www.xbrl.org/2003/linkbase" />
  <import schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" namespace="http://xbrl.org/2005/xbrldt" />
  <import schemaLocation="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd" namespace="http://fasb.org/us-gaap/2017-01-31" />
  <import schemaLocation="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd" namespace="http://xbrl.sec.gov/dei/2014-01-31" />
  <import schemaLocation="http://xbrl.fasb.org/us-gaap/2017/elts/us-types-2017-01-31.xsd" namespace="http://fasb.org/us-types/2017-01-31" />
  <import schemaLocation="http://www.xbrl.org/dtr/type/numeric-2009-12-16.xsd" namespace="http://www.xbrl.org/dtr/type/numeric" />
  <import schemaLocation="http://www.xbrl.org/dtr/type/nonNumeric-2009-12-16.xsd" namespace="http://www.xbrl.org/dtr/type/non-numeric" />
  <import schemaLocation="http://xbrl.sec.gov/country/2017/country-2017-01-31.xsd" namespace="http://xbrl.sec.gov/country/2017-01-31" />
  <import schemaLocation="http://xbrl.sec.gov/currency/2017/currency-2017-01-31.xsd" namespace="http://xbrl.sec.gov/currency/2017-01-31" />
  <import schemaLocation="http://xbrl.sec.gov/exch/2017/exch-2017-01-31.xsd" namespace="http://xbrl.sec.gov/exch/2017-01-31" />
  <import schemaLocation="http://xbrl.sec.gov/invest/2013/invest-2013-01-31.xsd" namespace="http://xbrl.sec.gov/invest/2013-01-31" />
  <import schemaLocation="http://xbrl.sec.gov/naics/2017/naics-2017-01-31.xsd" namespace="http://xbrl.sec.gov/naics/2017-01-31" />
  <import schemaLocation="http://xbrl.sec.gov/sic/2011/sic-2011-01-31.xsd" namespace="http://xbrl.sec.gov/sic/2011-01-31" />
  <import schemaLocation="http://xbrl.sec.gov/stpr/2011/stpr-2011-01-31.xsd" namespace="http://xbrl.sec.gov/stpr/2011-01-31" />
  <annotation>
    <appinfo>
      <link:roleType id="TemplateLink" roleURI="http://www.adtran.com/20180331/role/TemplateLink" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>00000 - Document - Template Link</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="adtn-20180331_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:title="Calculation Links, all" xlink:type="simple" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" />
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="adtn-20180331_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:title="Definition Links, all" xlink:type="simple" />
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="adtn-20180331_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:title="Label Links, all" xlink:type="simple" />
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="adtn-20180331_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:title="Presentation Links, all" xlink:type="simple" />
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DocumentDocumentAndEntityInformation" id="Role_DocumentDocumentAndEntityInformation">
        <link:definition>100000 - Document - Document and Entity Information</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/StatementConsolidatedBalanceSheetsUnaudited" id="Role_StatementConsolidatedBalanceSheetsUnaudited">
        <link:definition>100010 - Statement - Consolidated Balance Sheets (Unaudited)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/StatementConsolidatedBalanceSheetsUnauditedParenthetical" id="Role_StatementConsolidatedBalanceSheetsUnauditedParenthetical">
        <link:definition>100020 - Statement - Consolidated Balance Sheets (Unaudited) (Parenthetical)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/StatementConsolidatedStatementsOfIncomeUnaudited" id="Role_StatementConsolidatedStatementsOfIncomeUnaudited">
        <link:definition>100030 - Statement - Consolidated Statements of Income (Unaudited)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/StatementConsolidatedStatementsOfComprehensiveIncomeUnaudited" id="Role_StatementConsolidatedStatementsOfComprehensiveIncomeUnaudited">
        <link:definition>100040 - Statement - Consolidated Statements of Comprehensive Income (Unaudited)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/StatementConsolidatedStatementsOfCashFlowsUnaudited" id="Role_StatementConsolidatedStatementsOfCashFlowsUnaudited">
        <link:definition>100050 - Statement - Consolidated Statements of Cash Flows (Unaudited)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies" id="Role_DisclosureSummaryOfSignificantAccountingPolicies">
        <link:definition>100060 - Disclosure - Summary of Significant Accounting Policies</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureBusinessCombinations" id="Role_DisclosureBusinessCombinations">
        <link:definition>100070 - Disclosure - Business Combinations</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureRevenue" id="Role_DisclosureRevenue">
        <link:definition>100080 - Disclosure - Revenue</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureIncomeTaxes" id="Role_DisclosureIncomeTaxes">
        <link:definition>100090 - Disclosure - Income Taxes</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosurePensionBenefitPlan" id="Role_DisclosurePensionBenefitPlan">
        <link:definition>100100 - Disclosure - Pension Benefit Plan</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureStockBasedCompensation" id="Role_DisclosureStockBasedCompensation">
        <link:definition>100110 - Disclosure - Stock-Based Compensation</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureInvestments" id="Role_DisclosureInvestments">
        <link:definition>100120 - Disclosure - Investments</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureDerivativeInstrumentsAndHedgingActivities" id="Role_DisclosureDerivativeInstrumentsAndHedgingActivities">
        <link:definition>100130 - Disclosure - Derivative Instruments and Hedging Activities</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureInventory" id="Role_DisclosureInventory">
        <link:definition>100140 - Disclosure - Inventory</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureGoodwillAndIntangibleAssets" id="Role_DisclosureGoodwillAndIntangibleAssets">
        <link:definition>100150 - Disclosure - Goodwill and Intangible Assets</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureStockholdersEquity" id="Role_DisclosureStockholdersEquity">
        <link:definition>100160 - Disclosure - Stockholders&apos; Equity</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureEarningsPerShare" id="Role_DisclosureEarningsPerShare">
        <link:definition>100170 - Disclosure - Earnings Per Share</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureSegmentInformation" id="Role_DisclosureSegmentInformation">
        <link:definition>100180 - Disclosure - Segment Information</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureLiabilityForWarrantyReturns" id="Role_DisclosureLiabilityForWarrantyReturns">
        <link:definition>100190 - Disclosure - Liability for Warranty Returns</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureCommitmentsAndContingencies" id="Role_DisclosureCommitmentsAndContingencies">
        <link:definition>100200 - Disclosure - Commitments and Contingencies</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureSubsequentEvents" id="Role_DisclosureSubsequentEvents">
        <link:definition>100210 - Disclosure - Subsequent Events</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies" id="Role_DisclosureSummaryOfSignificantAccountingPoliciesPolicies">
        <link:definition>100220 - Disclosure - Summary of Significant Accounting Policies (Policies)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesTables" id="Role_DisclosureSummaryOfSignificantAccountingPoliciesTables">
        <link:definition>100230 - Disclosure - Summary of Significant Accounting Policies (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureBusinessCombinationsTables" id="Role_DisclosureBusinessCombinationsTables">
        <link:definition>100240 - Disclosure - Business Combinations (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureRevenueTables" id="Role_DisclosureRevenueTables">
        <link:definition>100250 - Disclosure - Revenue (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosurePensionBenefitPlanTables" id="Role_DisclosurePensionBenefitPlanTables">
        <link:definition>100260 - Disclosure - Pension Benefit Plan (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureStockBasedCompensationTables" id="Role_DisclosureStockBasedCompensationTables">
        <link:definition>100270 - Disclosure - Stock-Based Compensation (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureInvestmentsTables" id="Role_DisclosureInvestmentsTables">
        <link:definition>100280 - Disclosure - Investments (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureDerivativeInstrumentsAndHedgingActivitiesTables" id="Role_DisclosureDerivativeInstrumentsAndHedgingActivitiesTables">
        <link:definition>100290 - Disclosure - Derivative Instruments and Hedging Activities (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureInventoryTables" id="Role_DisclosureInventoryTables">
        <link:definition>100300 - Disclosure - Inventory (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsTables" id="Role_DisclosureGoodwillAndIntangibleAssetsTables">
        <link:definition>100310 - Disclosure - Goodwill and Intangible Assets (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureStockholdersEquityTables" id="Role_DisclosureStockholdersEquityTables">
        <link:definition>100320 - Disclosure - Stockholders&apos; Equity (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureEarningsPerShareTables" id="Role_DisclosureEarningsPerShareTables">
        <link:definition>100330 - Disclosure - Earnings Per Share (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureSegmentInformationTables" id="Role_DisclosureSegmentInformationTables">
        <link:definition>100340 - Disclosure - Segment Information (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureLiabilityForWarrantyReturnsTables" id="Role_DisclosureLiabilityForWarrantyReturnsTables">
        <link:definition>100350 - Disclosure - Liability for Warranty Returns (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesScheduleOfCumulativeEffectOfChangesMadeToConsolidatedBalanceSheetDetail" id="Role_DisclosureSummaryOfSignificantAccountingPoliciesScheduleOfCumulativeEffectOfChangesMadeToConsolidatedBalanceSheetDetail">
        <link:definition>100360 - Disclosure - Summary of Significant Accounting Policies - Schedule of Cumulative Effect of Changes made to Consolidated Balance Sheet (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesSummaryOfImpactOfAdoptionOfASU201409AndRelatedAsusDetail" id="Role_DisclosureSummaryOfSignificantAccountingPoliciesSummaryOfImpactOfAdoptionOfASU201409AndRelatedAsusDetail">
        <link:definition>100370 - Disclosure - Summary of Significant Accounting Policies - Summary of Impact of Adoption of ASU 2014-09 and Related ASUs (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetail" id="Role_DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetail">
        <link:definition>100380 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureBusinessCombinationsAdditionalInformationDetail" id="Role_DisclosureBusinessCombinationsAdditionalInformationDetail">
        <link:definition>100390 - Disclosure - Business Combinations - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureBusinessCombinationsPreliminaryAllocationOfPurchasePriceToEstimatedFairValueOfAssetsAcquiredDetail" id="Role_DisclosureBusinessCombinationsPreliminaryAllocationOfPurchasePriceToEstimatedFairValueOfAssetsAcquiredDetail">
        <link:definition>100400 - Disclosure - Business Combinations - Preliminary Allocation of the Purchase Price to the Estimated Fair Value of the Assets Acquired (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureBusinessCombinationsSummaryOfActualRevenueAndNetLossIncludedInConsolidatedStatementsOfIncomeDetail" id="Role_DisclosureBusinessCombinationsSummaryOfActualRevenueAndNetLossIncludedInConsolidatedStatementsOfIncomeDetail">
        <link:definition>100410 - Disclosure - Business Combinations - Summary of Actual Revenue and Net Loss Included in Consolidated Statements of Income (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureBusinessCombinationsDetailsOfAcquiredIntangibleAssetsDetail" id="Role_DisclosureBusinessCombinationsDetailsOfAcquiredIntangibleAssetsDetail">
        <link:definition>100420 - Disclosure - Business Combinations - Details of the Acquired Intangible Assets (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureBusinessCombinationsSummaryOfUnauditedSupplementalProFormaInformationDetail" id="Role_DisclosureBusinessCombinationsSummaryOfUnauditedSupplementalProFormaInformationDetail">
        <link:definition>100430 - Disclosure - Business Combinations - Summary of Unaudited Supplemental Pro Forma Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureRevenueAdditionalInformationDetail" id="Role_DisclosureRevenueAdditionalInformationDetail">
        <link:definition>100440 - Disclosure - Revenue - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureRevenueInformationAboutReceivablesContractAssetsAndUnearnedRevenueFromContractsWithCustomersDetail" id="Role_DisclosureRevenueInformationAboutReceivablesContractAssetsAndUnearnedRevenueFromContractsWithCustomersDetail">
        <link:definition>100450 - Disclosure - Revenue - Information about Receivables, Contract Assets, and Unearned Revenue from Contracts with Customers (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureRevenueDisaggregateOfRevenueByMajorSourceDetail" id="Role_DisclosureRevenueDisaggregateOfRevenueByMajorSourceDetail">
        <link:definition>100460 - Disclosure - Revenue - Disaggregate of Revenue by Major Source (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureIncomeTaxesAdditionalInformationDetail" id="Role_DisclosureIncomeTaxesAdditionalInformationDetail">
        <link:definition>100470 - Disclosure - Income Taxes - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosurePensionBenefitPlanSummarizationOfComponentsOfNetPeriodicPensionCostDetail" id="Role_DisclosurePensionBenefitPlanSummarizationOfComponentsOfNetPeriodicPensionCostDetail">
        <link:definition>100480 - Disclosure - Pension Benefit Plan - Summarization of Components of Net Periodic Pension Cost (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureStockBasedCompensationStockBasedCompensationExpenseRelatedToStockOptionsPerformanceStockUnitsPsusRestrictedStockUnitsRsusAndRestrictedStockDetail" id="Role_DisclosureStockBasedCompensationStockBasedCompensationExpenseRelatedToStockOptionsPerformanceStockUnitsPsusRestrictedStockUnitsRsusAndRestrictedStockDetail">
        <link:definition>100490 - Disclosure - Stock-Based Compensation - Stock-Based Compensation Expense Related to Stock Options, Performance Stock Units (PSUs), Restricted Stock Units (RSUs) and Restricted Stock (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureStockBasedCompensationSummaryOfStockOptionsOutstandingDetail" id="Role_DisclosureStockBasedCompensationSummaryOfStockOptionsOutstandingDetail">
        <link:definition>100500 - Disclosure - Stock-Based Compensation - Summary of Stock Options Outstanding (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureStockBasedCompensationStockOptionsAdditionalInformationDetail" id="Role_DisclosureStockBasedCompensationStockOptionsAdditionalInformationDetail">
        <link:definition>100510 - Disclosure - Stock-Based Compensation (Stock Options) - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureStockBasedCompensationSummaryOfPsusRsusAndRestrictedStockOutstandingDetail" id="Role_DisclosureStockBasedCompensationSummaryOfPsusRsusAndRestrictedStockOutstandingDetail">
        <link:definition>100520 - Disclosure - Stock-Based Compensation - Summary of PSUs, RSUs and Restricted Stock Outstanding (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureStockBasedCompensationPsusRsusAndRestrictedStockAdditionalInformationDetail" id="Role_DisclosureStockBasedCompensationPsusRsusAndRestrictedStockAdditionalInformationDetail">
        <link:definition>100530 - Disclosure - Stock-Based Compensation (PSUs, RSUs and Restricted Stock) - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureInvestmentsDebtSecuritiesAndOtherInvestmentsRecordedAtEitherFairValueOrCostDetail" id="Role_DisclosureInvestmentsDebtSecuritiesAndOtherInvestmentsRecordedAtEitherFairValueOrCostDetail">
        <link:definition>100540 - Disclosure - Investments - Debt Securities and Other Investments, Recorded at Either Fair Value or Cost (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureInvestmentsContractualMaturitiesOfDebtSecuritiesDetail" id="Role_DisclosureInvestmentsContractualMaturitiesOfDebtSecuritiesDetail">
        <link:definition>100550 - Disclosure - Investments - Contractual Maturities of Debt Securities (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureInvestmentsGrossRealizedGainsAndLossesOnSaleOfDebtSecuritiesDetail" id="Role_DisclosureInvestmentsGrossRealizedGainsAndLossesOnSaleOfDebtSecuritiesDetail">
        <link:definition>100560 - Disclosure - Investments - Gross Realized Gains and Losses on Sale of Debt Securities (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureInvestmentsAdditionalInformationDetail" id="Role_DisclosureInvestmentsAdditionalInformationDetail">
        <link:definition>100570 - Disclosure - Investments - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureInvestmentsRealizedAndUnrealizedGainsAndLossesForMarketableEquitySecuritiesDetail" id="Role_DisclosureInvestmentsRealizedAndUnrealizedGainsAndLossesForMarketableEquitySecuritiesDetail">
        <link:definition>100580 - Disclosure - Investments - Realized and Unrealized Gains and Losses for Marketable Equity Securities (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureInvestmentsFairValueMeasurementsOfCashEquivalentsAndInvestmentsDetail" id="Role_DisclosureInvestmentsFairValueMeasurementsOfCashEquivalentsAndInvestmentsDetail">
        <link:definition>100590 - Disclosure - Investments - Fair Value Measurements of Cash Equivalents and Investments (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureDerivativeInstrumentsAndHedgingActivitiesAdditionalInformationDetail" id="Role_DisclosureDerivativeInstrumentsAndHedgingActivitiesAdditionalInformationDetail">
        <link:definition>100600 - Disclosure - Derivative Instruments and Hedging Activities - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureDerivativeInstrumentsAndHedgingActivitiesScheduleOfChangeInFairValuesOfDerivativeInstrumentsRecordedInConsolidatedStatementsOfIncomeDetail" id="Role_DisclosureDerivativeInstrumentsAndHedgingActivitiesScheduleOfChangeInFairValuesOfDerivativeInstrumentsRecordedInConsolidatedStatementsOfIncomeDetail">
        <link:definition>100610 - Disclosure - Derivative Instruments and Hedging Activities - Schedule of Change in Fair Values of Derivative Instruments Recorded in Consolidated Statements of Income (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureDerivativeInstrumentsAndHedgingActivitiesScheduleOfChangeInDerivativesDesignatedHedgingInstrumentsRecordedInOtherComprehensiveIncomeOCIAndReclassifiedToIncomeNetOfTaxDetail" id="Role_DisclosureDerivativeInstrumentsAndHedgingActivitiesScheduleOfChangeInDerivativesDesignatedHedgingInstrumentsRecordedInOtherComprehensiveIncomeOCIAndReclassifiedToIncomeNetOfTaxDetail">
        <link:definition>100620 - Disclosure - Derivative Instruments and Hedging Activities - Schedule of Change in Derivatives Designated Hedging Instruments Recorded in Other Comprehensive Income (OCI) and Reclassified to Income, Net of Tax (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureInventoryComponentsOfInventoryDetail" id="Role_DisclosureInventoryComponentsOfInventoryDetail">
        <link:definition>100630 - Disclosure - Inventory - Components of Inventory (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureInventoryAdditionalInformationDetail" id="Role_DisclosureInventoryAdditionalInformationDetail">
        <link:definition>100640 - Disclosure - Inventory - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsAdditionalInformationDetail" id="Role_DisclosureGoodwillAndIntangibleAssetsAdditionalInformationDetail">
        <link:definition>100650 - Disclosure - Goodwill and Intangible Assets - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsSummaryOfIntangibleAssetsDetail" id="Role_DisclosureGoodwillAndIntangibleAssetsSummaryOfIntangibleAssetsDetail">
        <link:definition>100660 - Disclosure - Goodwill and Intangible Assets - Summary of Intangible Assets (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsEstimatedFutureAmortizationExpenseRelatedToIntangibleAssetsDetail" id="Role_DisclosureGoodwillAndIntangibleAssetsEstimatedFutureAmortizationExpenseRelatedToIntangibleAssetsDetail">
        <link:definition>100670 - Disclosure - Goodwill and Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureStockholdersEquitySummaryOfChangesInStockholdersEquityDetail" id="Role_DisclosureStockholdersEquitySummaryOfChangesInStockholdersEquityDetail">
        <link:definition>100680 - Disclosure - Stockholders&apos; Equity - Summary of Changes in Stockholders&apos; Equity (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail" id="Role_DisclosureStockholdersEquityAdditionalInformationDetail">
        <link:definition>100690 - Disclosure - Stockholders&apos; Equity - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureStockholdersEquityCashDividendsDetail" id="Role_DisclosureStockholdersEquityCashDividendsDetail">
        <link:definition>100700 - Disclosure - Stockholders&apos; Equity - Cash Dividends (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureStockholdersEquityChangesInAccumulatedOtherComprehensiveIncomeNetOfTaxByComponentDetail" id="Role_DisclosureStockholdersEquityChangesInAccumulatedOtherComprehensiveIncomeNetOfTaxByComponentDetail">
        <link:definition>100710 - Disclosure - Stockholders&apos; Equity - Changes in Accumulated Other Comprehensive Income, Net of Tax by Component (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureStockholdersEquityReclassificationsOutOfAccumulatedOtherComprehensiveIncomeDetail" id="Role_DisclosureStockholdersEquityReclassificationsOutOfAccumulatedOtherComprehensiveIncomeDetail">
        <link:definition>100720 - Disclosure - Stockholders&apos; Equity - Reclassifications Out of Accumulated Other Comprehensive Income (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureStockholdersEquityTaxEffectsRelatedToChangeInEachComponentOfOtherComprehensiveIncomeDetail" id="Role_DisclosureStockholdersEquityTaxEffectsRelatedToChangeInEachComponentOfOtherComprehensiveIncomeDetail">
        <link:definition>100730 - Disclosure - Stockholders&apos; Equity - Tax Effects Related to the Change in Each Component of Other Comprehensive Income (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureEarningsPerShareSummaryOfCalculationOfBasicAndDilutedEarningsPerShareDetail" id="Role_DisclosureEarningsPerShareSummaryOfCalculationOfBasicAndDilutedEarningsPerShareDetail">
        <link:definition>100740 - Disclosure - Earnings Per Share - Summary of Calculation of Basic and Diluted Earnings Per Share (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureEarningsPerShareAdditionalInformationDetail" id="Role_DisclosureEarningsPerShareAdditionalInformationDetail">
        <link:definition>100750 - Disclosure - Earnings Per Share - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureSegmentInformationAdditionalInformationDetail" id="Role_DisclosureSegmentInformationAdditionalInformationDetail">
        <link:definition>100760 - Disclosure - Segment Information - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureSegmentInformationSalesAndGrossProfitOfReportableSegmentsDetail" id="Role_DisclosureSegmentInformationSalesAndGrossProfitOfReportableSegmentsDetail">
        <link:definition>100770 - Disclosure - Segment Information - Sales and Gross Profit of Reportable Segments (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureSegmentInformationSalesInformationByCategoryDetail" id="Role_DisclosureSegmentInformationSalesInformationByCategoryDetail">
        <link:definition>100780 - Disclosure - Segment Information - Sales Information by Category (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureLiabilityForWarrantyReturnsAdditionalInformationDetail" id="Role_DisclosureLiabilityForWarrantyReturnsAdditionalInformationDetail">
        <link:definition>100790 - Disclosure - Liability for Warranty Returns - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureLiabilityForWarrantyReturnsSummaryOfWarrantyExpenseAndWriteOffActivityDetail" id="Role_DisclosureLiabilityForWarrantyReturnsSummaryOfWarrantyExpenseAndWriteOffActivityDetail">
        <link:definition>100800 - Disclosure - Liability for Warranty Returns - Summary of Warranty Expense and Write-Off Activity (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureCommitmentsAndContingenciesAdditionalInformationDetail" id="Role_DisclosureCommitmentsAndContingenciesAdditionalInformationDetail">
        <link:definition>100810 - Disclosure - Commitments and Contingencies - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.adtran.com/20180331/taxonomy/role/DisclosureSubsequentEventsAdditionalInformationDetail" id="Role_DisclosureSubsequentEventsAdditionalInformationDetail">
        <link:definition>100820 - Disclosure - Subsequent Events - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
    </appinfo>
  </annotation>
  <element id="adtn_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIRetainedEarningsBeforeTax" name="OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIRetainedEarningsBeforeTax" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <element id="adtn_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIRetainedEarningsTax" name="OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIRetainedEarningsTax" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <element id="adtn_DocumentAndEntityInformationAbstract" name="DocumentAndEntityInformationAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_SummaryOfActualRevenueAndNetLossIncludedInConsolidatedStatementsOfIncomeTableTextBlock" name="SummaryOfActualRevenueAndNetLossIncludedInConsolidatedStatementsOfIncomeTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="adtn_ScheduleOfShareBasedCompensationPerformanceStockUnitsRestrictedStockUnitsAndRestrictedStockActivityTableTextBlock" name="ScheduleOfShareBasedCompensationPerformanceStockUnitsRestrictedStockUnitsAndRestrictedStockActivityTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="adtn_SummaryOfSignificantAccountingPolicyLineItems" name="SummaryOfSignificantAccountingPolicyLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_SummaryOfSignificantAccountingPolicyTable" name="SummaryOfSignificantAccountingPolicyTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_AccountingStandardsUpdate201707Member" name="AccountingStandardsUpdate201707Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_SumitomoElectricLightwaveCorpSNorthAmericanEPONBusinessMember" name="SumitomoElectricLightwaveCorpSNorthAmericanEPONBusinessMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_SupplierRelationshipMember" name="SupplierRelationshipMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_BusinessCombinationAcquisitionAndIntegrationRelatedCostsAndAmortizationOfAcquiredIntangibles" name="BusinessCombinationAcquisitionAndIntegrationRelatedCostsAndAmortizationOfAcquiredIntangibles" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <element id="adtn_RevenueLineItems" name="RevenueLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_RevenueTable" name="RevenueTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_LessorSalesTypeLeaseArrangementTermsForNetworkEquipment" name="LessorSalesTypeLeaseArrangementTermsForNetworkEquipment" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="adtn_MaintenanceServicePeriods" name="MaintenanceServicePeriods" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="adtn_NetworkSolutionsMember" name="NetworkSolutionsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_ServicesAndSupportMember" name="ServicesAndSupportMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_AccessAndAggregationMember" name="AccessAndAggregationMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_CustomerDevicesMember" name="CustomerDevicesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_TraditionalAndOtherProductsMember" name="TraditionalAndOtherProductsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_UnvestedStockOptionsMember" name="UnvestedStockOptionsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_PerformanceStockUnitsMember" name="PerformanceStockUnitsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_MarketBasedPerformanceStockUnitsRestrictedStockUnitsAndRestrictedStockMember" name="MarketBasedPerformanceStockUnitsRestrictedStockUnitsAndRestrictedStockMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_PerformanceBasedPerformanceStockUnitsMember" name="PerformanceBasedPerformanceStockUnitsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_PerformanceBasedPerformanceStockUnitsAwardsMember" name="PerformanceBasedPerformanceStockUnitsAwardsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_AmortizedCostAndFairValueDebtSecuritiesAbstract" name="AmortizedCostAndFairValueDebtSecuritiesAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughTwoYearsFairValue" name="AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughTwoYearsFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <element id="adtn_AvailableForSaleSecuritiesDebtMaturitiesAfterTwoThroughThreeYearsFairValue" name="AvailableForSaleSecuritiesDebtMaturitiesAfterTwoThroughThreeYearsFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <element id="adtn_AvailableForSaleSecuritiesDebtMaturitiesAfterThreeThroughFiveYearsFairValue" name="AvailableForSaleSecuritiesDebtMaturitiesAfterThreeThroughFiveYearsFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <element id="adtn_AvailableForSaleSecuritiesGrossRealizedAndUnrealizedGainLossNet" name="AvailableForSaleSecuritiesGrossRealizedAndUnrealizedGainLossNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <element id="adtn_MarketableEquitySecuritiesVariousIndustriesMember" name="MarketableEquitySecuritiesVariousIndustriesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_DeferredCompensationPlanAssetsMember" name="DeferredCompensationPlanAssetsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_OtherIncomeExpenseMember" name="OtherIncomeExpenseMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_RawMaterialsMember" name="RawMaterialsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_FinishedGoodsMember" name="FinishedGoodsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_LicensedTechnologyMember" name="LicensedTechnologyMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_DividendsAccruedForUnvestedRestrictedStockUnits" name="DividendsAccruedForUnvestedRestrictedStockUnits" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <element id="adtn_CashDividendsPaidInFebruaryMember" name="CashDividendsPaidInFebruaryMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_ImpairmentLossMember" name="ImpairmentLossMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIRetainedEarningsNetOfTax" name="OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIRetainedEarningsNetOfTax" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <element id="adtn_NumberOfProductCategories" name="NumberOfProductCategories" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="adtn_AccessAndAggregationsMember" name="AccessAndAggregationsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_ProductWarrantyAccrualIncreaseDecreaseForWarrantiesIssued" name="ProductWarrantyAccrualIncreaseDecreaseForWarrantiesIssued" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <element id="adtn_ProductWarrantyAccrualIncreaseDecreaseForPayments" name="ProductWarrantyAccrualIncreaseDecreaseForPayments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <element id="adtn_NumberOfPrivateEquityFunds" name="NumberOfPrivateEquityFunds" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <element id="adtn_CommitmentsTowardsPrivateEquityFunds" name="CommitmentsTowardsPrivateEquityFunds" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <element id="adtn_ContingenciesAndCommitmentsLineItems" name="ContingenciesAndCommitmentsLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_ContingenciesAndCommitmentsTable" name="ContingenciesAndCommitmentsTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="adtn_InvestmentCommitmentsMember" name="InvestmentCommitmentsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
</schema>
