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<!-- DFIN ActiveDisclosure(SM) XBRL Schema Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date      : 2020-05-08T13:58:31.9882257+00:00 -->
<!-- Version            : 5.0.1.385 -->
<!-- Package ID         : d5686606cf7248079b6b6fc81d41995a -->
<!-- Copyright (c) 2020 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
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  <xsd:element id="adtn_InterestAndDividendIncomeMember" name="InterestAndDividendIncomeMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="adtn_EquityMethodInvestmentsAndCostMethodInvestmentsAbstract" name="EquityMethodInvestmentsAndCostMethodInvestmentsAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="adtn_OtherComprehensiveIncomeLossNetOfTaxDueToChangesInAccountingStandard" name="OtherComprehensiveIncomeLossNetOfTaxDueToChangesInAccountingStandard" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="adtn_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIRetainedEarningsNetOfTax" name="OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIRetainedEarningsNetOfTax" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="adtn_UnvestedStockOptionsPerformanceStockUnitsRestrictedStockUnitsAndRestrictedStockMember" name="UnvestedStockOptionsPerformanceStockUnitsRestrictedStockUnitsAndRestrictedStockMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="adtn_AccessAndAggregationsMember" name="AccessAndAggregationsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="adtn_ProductWarrantyAccrualIncreaseDecreaseForWarrantiesIssued" name="ProductWarrantyAccrualIncreaseDecreaseForWarrantiesIssued" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="adtn_NumberOfOfficers" name="NumberOfOfficers" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="adtn_ContingenciesAndCommitmentsLineItems" name="ContingenciesAndCommitmentsLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="adtn_ContingenciesAndCommitmentsTable" name="ContingenciesAndCommitmentsTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="adtn_CurrentExecutiveOfficersMember" name="CurrentExecutiveOfficersMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="adtn_FormerExecutiveOfficersMember" name="FormerExecutiveOfficersMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="adtn_InvestmentCommitmentsMember" name="InvestmentCommitmentsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="adtn_CommitmentsRelatedToPerformanceBonds" name="CommitmentsRelatedToPerformanceBonds" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="adtn_CommitmentsRelatedToPerformanceBondsExpirationMonthAndYear" name="CommitmentsRelatedToPerformanceBondsExpirationMonthAndYear" type="xbrli:gYearMonthItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="adtn_NumberOfPrivateEquityFunds" name="NumberOfPrivateEquityFunds" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="adtn_CommitmentsTowardsPrivateEquityFunds" name="CommitmentsTowardsPrivateEquityFunds" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
</xsd:schema>
