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

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2022 Workiva-->
<!--r:368d367d-beb3-477f-87b6-b6cfd3b1dc77,g:0bc56581-7549-4bc1-a0c5-dd60a0bc219c-->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:arwr="http://www.arrowheadresearch.com/20220630" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2020-01-21" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.arrowheadresearch.com/20220630">
  <xs:import namespace="http://fasb.org/srt/2022" schemaLocation="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd"/>
  <xs:import namespace="http://fasb.org/us-gaap/2022" schemaLocation="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.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://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/dei/2022" schemaLocation="https://xbrl.sec.gov/dei/2022/dei-2022.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/stpr/2022" schemaLocation="https://xbrl.sec.gov/stpr/2022/stpr-2022.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="arwr-20220630_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="arwr-20220630_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="arwr-20220630_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" 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="arwr-20220630_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:type="simple"/>
      <link:roleType id="Cover" roleURI="http://www.arrowheadresearch.com/role/Cover">
        <link:definition>0001001 - 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="ConsolidatedBalanceSheets" roleURI="http://www.arrowheadresearch.com/role/ConsolidatedBalanceSheets">
        <link:definition>1001002 - 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.arrowheadresearch.com/role/ConsolidatedBalanceSheetsParenthetical">
        <link:definition>1002003 - 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="ConsolidatedStatementsofOperationsandComprehensiveIncomeLoss" roleURI="http://www.arrowheadresearch.com/role/ConsolidatedStatementsofOperationsandComprehensiveIncomeLoss">
        <link:definition>1003004 - Statement - Consolidated Statements of Operations and 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="ConsolidatedStatementsofStockholdersEquityandNoncontrollingInterest" roleURI="http://www.arrowheadresearch.com/role/ConsolidatedStatementsofStockholdersEquityandNoncontrollingInterest">
        <link:definition>1004005 - Statement - Consolidated Statements of Stockholders&#8217; Equity and Noncontrolling Interest</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.arrowheadresearch.com/role/ConsolidatedStatementsofCashFlows">
        <link:definition>1005006 - 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="OrganizationandSignificantAccountingPolicies" roleURI="http://www.arrowheadresearch.com/role/OrganizationandSignificantAccountingPolicies">
        <link:definition>2101101 - Disclosure - Organization and 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="OrganizationandSignificantAccountingPoliciesPolicies" roleURI="http://www.arrowheadresearch.com/role/OrganizationandSignificantAccountingPoliciesPolicies">
        <link:definition>2202201 - Disclosure - Organization and 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="OrganizationandSignificantAccountingPoliciesAdditionalInformationDetail" roleURI="http://www.arrowheadresearch.com/role/OrganizationandSignificantAccountingPoliciesAdditionalInformationDetail">
        <link:definition>2403401 - Disclosure - Organization and Significant Accounting Policies - Additional Information (Detail)</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="CollaborationandLicenseAgreements" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreements">
        <link:definition>2104102 - Disclosure - Collaboration and License Agreements</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="CollaborationandLicenseAgreementsAmgenIncAdditionalInformationDetail" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreementsAmgenIncAdditionalInformationDetail">
        <link:definition>2405402 - Disclosure - Collaboration and License Agreements - Amgen, Inc - Additional Information (Detail)</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="CollaborationandLicenseAgreementsJanssenPharmaceuticalsIncAdditionalInformationDetail" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreementsJanssenPharmaceuticalsIncAdditionalInformationDetail">
        <link:definition>2406403 - Disclosure - Collaboration and License Agreements - Janssen Pharmaceuticals, Inc - Additional Information (Detail)</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="CollaborationandLicenseAgreementsTakedaPharmaceuticalsUSAIncAdditionalInformationDetail" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreementsTakedaPharmaceuticalsUSAIncAdditionalInformationDetail">
        <link:definition>2407404 - Disclosure - Collaboration and License Agreements - Takeda Pharmaceuticals U.S.A., Inc - Additional Information (Detail)</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="CollaborationandLicenseAgreementsHorizonTherapeuticsIrelandDACAdditionalInformationDetail" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreementsHorizonTherapeuticsIrelandDACAdditionalInformationDetail">
        <link:definition>2408405 - Disclosure - Collaboration and License Agreements - Horizon Therapeutics Ireland DAC - Additional Information (Detail)</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="CollaborationandLicenseAgreementsGlaxosmithklineIntellectualPropertyNo3LimitedAdditionalInformationDetail" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreementsGlaxosmithklineIntellectualPropertyNo3LimitedAdditionalInformationDetail">
        <link:definition>2409406 - Disclosure - Collaboration and License Agreements - Glaxosmithkline Intellectual Property (No. 3) Limited - Additional Information (Detail)</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="CollaborationandLicenseAgreementsJointVentureandLicenseAgreementwithVisirnaTherapeuticsIncAdditionalInformationDetailDetails" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreementsJointVentureandLicenseAgreementwithVisirnaTherapeuticsIncAdditionalInformationDetailDetails">
        <link:definition>2410407 - Disclosure - Collaboration and License Agreements - Joint Venture and License Agreement with Visirna Therapeutics, Inc. - Additional Information (Detail) (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="PropertyandEquipment" roleURI="http://www.arrowheadresearch.com/role/PropertyandEquipment">
        <link:definition>2111103 - Disclosure - Property and Equipment</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="PropertyandEquipmentTables" roleURI="http://www.arrowheadresearch.com/role/PropertyandEquipmentTables">
        <link:definition>2312301 - Disclosure - Property and Equipment (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="PropertyandEquipmentSummaryofPropertyandEquipmentDetail" roleURI="http://www.arrowheadresearch.com/role/PropertyandEquipmentSummaryofPropertyandEquipmentDetail">
        <link:definition>2413408 - Disclosure - Property and Equipment - Summary of Property and Equipment (Detail)</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="PropertyandEquipmentAdditionalInformationDetail" roleURI="http://www.arrowheadresearch.com/role/PropertyandEquipmentAdditionalInformationDetail">
        <link:definition>2414409 - Disclosure - Property and Equipment - Additional Information (Detail)</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="Investments" roleURI="http://www.arrowheadresearch.com/role/Investments">
        <link:definition>2115104 - Disclosure - Investments</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="InvestmentsTables" roleURI="http://www.arrowheadresearch.com/role/InvestmentsTables">
        <link:definition>2316302 - Disclosure - Investments (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="InvestmentsSummaryofShorttermandLongtermInvestmentsandMarketableSecuritiesDetail" roleURI="http://www.arrowheadresearch.com/role/InvestmentsSummaryofShorttermandLongtermInvestmentsandMarketableSecuritiesDetail">
        <link:definition>2417410 - Disclosure - Investments - Summary of Short-term and Long-term Investments and Marketable Securities (Detail)</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="InvestmentsSummaryofShorttermandLongtermInvestmentsandMarketableSecuritiesDetail_1" roleURI="http://www.arrowheadresearch.com/role/InvestmentsSummaryofShorttermandLongtermInvestmentsandMarketableSecuritiesDetail_1">
        <link:definition>2417410 - Disclosure - Investments - Summary of Short-term and Long-term Investments and Marketable Securities (Detail)</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="IntangibleAssets" roleURI="http://www.arrowheadresearch.com/role/IntangibleAssets">
        <link:definition>2118105 - Disclosure - 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="IntangibleAssetsTables" roleURI="http://www.arrowheadresearch.com/role/IntangibleAssetsTables">
        <link:definition>2319303 - Disclosure - 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="IntangibleAssetsAdditionalInformationDetail" roleURI="http://www.arrowheadresearch.com/role/IntangibleAssetsAdditionalInformationDetail">
        <link:definition>2420411 - Disclosure - Intangible Assets - Additional Information (Detail)</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="IntangibleAssetsScheduleofIntangibleAssetsDetail" roleURI="http://www.arrowheadresearch.com/role/IntangibleAssetsScheduleofIntangibleAssetsDetail">
        <link:definition>2421412 - Disclosure - Intangible Assets - Schedule of Intangible Assets (Detail)</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="StockholdersEquity" roleURI="http://www.arrowheadresearch.com/role/StockholdersEquity">
        <link:definition>2122106 - Disclosure - Stockholders' 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="StockholdersEquityAdditionalInformationDetail" roleURI="http://www.arrowheadresearch.com/role/StockholdersEquityAdditionalInformationDetail">
        <link:definition>2423413 - Disclosure - Stockholders' Equity - Additional Information (Detail)</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.arrowheadresearch.com/role/CommitmentsandContingencies">
        <link:definition>2124107 - 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="CommitmentsandContingenciesAdditionalInformationDetail" roleURI="http://www.arrowheadresearch.com/role/CommitmentsandContingenciesAdditionalInformationDetail">
        <link:definition>2425414 - Disclosure - Commitments and Contingencies - Additional Information (Detail)</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.arrowheadresearch.com/role/Leases">
        <link:definition>2126108 - 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="LeasesTables" roleURI="http://www.arrowheadresearch.com/role/LeasesTables">
        <link:definition>2327304 - 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="LeasesAdditionalInformationDetail" roleURI="http://www.arrowheadresearch.com/role/LeasesAdditionalInformationDetail">
        <link:definition>2428415 - Disclosure - Leases - Additional Information (Detail)</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="LeasesSummaryofMaturitiesofOperatingLeaseLiabilitiesonanUndiscountedBasisDetail" roleURI="http://www.arrowheadresearch.com/role/LeasesSummaryofMaturitiesofOperatingLeaseLiabilitiesonanUndiscountedBasisDetail">
        <link:definition>2429416 - Disclosure - Leases - Summary of Maturities of Operating Lease Liabilities on an Undiscounted Basis (Detail)</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="LeasesSummaryofMaturitiesofOperatingLeaseLiabilitiesonanUndiscountedBasisDetail_1" roleURI="http://www.arrowheadresearch.com/role/LeasesSummaryofMaturitiesofOperatingLeaseLiabilitiesonanUndiscountedBasisDetail_1">
        <link:definition>2429416 - Disclosure - Leases - Summary of Maturities of Operating Lease Liabilities on an Undiscounted Basis (Detail)</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="StockBasedCompensation" roleURI="http://www.arrowheadresearch.com/role/StockBasedCompensation">
        <link:definition>2130109 - Disclosure - Stock-Based Compensation</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="StockBasedCompensationTables" roleURI="http://www.arrowheadresearch.com/role/StockBasedCompensationTables">
        <link:definition>2331305 - Disclosure - Stock-Based Compensation (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="StockBasedCompensationAdditionalInformationDetail" roleURI="http://www.arrowheadresearch.com/role/StockBasedCompensationAdditionalInformationDetail">
        <link:definition>2432417 - Disclosure - Stock-Based Compensation - Additional Information (Detail)</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="StockBasedCompensationSummarizeInformationaboutStockOptionsDetail" roleURI="http://www.arrowheadresearch.com/role/StockBasedCompensationSummarizeInformationaboutStockOptionsDetail">
        <link:definition>2433418 - Disclosure - Stock-Based Compensation - Summarize Information about Stock Options (Detail)</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="StockBasedCompensationAssumptionsUsedtoValueStockOptionsDetail" roleURI="http://www.arrowheadresearch.com/role/StockBasedCompensationAssumptionsUsedtoValueStockOptionsDetail">
        <link:definition>2434419 - Disclosure - Stock-Based Compensation - Assumptions Used to Value Stock Options (Detail)</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="StockBasedCompensationSummaryofRSUsActivityDetail" roleURI="http://www.arrowheadresearch.com/role/StockBasedCompensationSummaryofRSUsActivityDetail">
        <link:definition>2435420 - Disclosure - Stock-Based Compensation - Summary of RSUs Activity (Detail)</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.arrowheadresearch.com/role/FairValueMeasurements">
        <link:definition>2136110 - 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="FairValueMeasurementsTables" roleURI="http://www.arrowheadresearch.com/role/FairValueMeasurementsTables">
        <link:definition>2337306 - 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="FairValueMeasurementsFairValueMeasurementsforAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetail" roleURI="http://www.arrowheadresearch.com/role/FairValueMeasurementsFairValueMeasurementsforAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetail">
        <link:definition>2438421 - Disclosure - Fair Value Measurements - Fair Value Measurements for Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail)</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="SubsequentEvents" roleURI="http://www.arrowheadresearch.com/role/SubsequentEvents">
        <link:definition>2139111 - Disclosure - Subsequent Events</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="arwr_CashReceivedAsDueUnderCollaborationAgreement" abstract="false" name="CashReceivedAsDueUnderCollaborationAgreement" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_AmgenIncorporatedMember" abstract="true" name="AmgenIncorporatedMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_MarketableSecuritiesMember" abstract="true" name="MarketableSecuritiesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_PerformanceObligationRelatedToAgreementUpfrontPayment" abstract="false" name="PerformanceObligationRelatedToAgreementUpfrontPayment" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_NumberOfOptionsToRenew" abstract="false" name="NumberOfOptionsToRenew" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="arwr_SalesRelatedMilestonePayments" abstract="false" name="SalesRelatedMilestonePayments" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_TwoThousandsThirteenIncentivePlanMember" abstract="true" name="TwoThousandsThirteenIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_OlpasiranAgreementMember" abstract="true" name="OlpasiranAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_LaboratoryAndOfficeFacilityMember" abstract="true" name="LaboratoryAndOfficeFacilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_MilestonePaymentReceivableAtStartOfPhaseTwo" abstract="false" name="MilestonePaymentReceivableAtStartOfPhaseTwo" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_ExpectedPaymentsOfLeaseholdImprovementsNetOfTenantImprovementAllowances" abstract="false" name="ExpectedPaymentsOfLeaseholdImprovementsNetOfTenantImprovementAllowances" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_DeferredRevenueMember" abstract="true" name="DeferredRevenueMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_TwoThousandFourEquityIncentivePlanTwoThousandThirteenEquityIncentivePlanTwoThousandTwentyOneEquityIncentivePlanAndInducementGrantsMember" abstract="true" name="TwoThousandFourEquityIncentivePlanTwoThousandThirteenEquityIncentivePlanTwoThousandTwentyOneEquityIncentivePlanAndInducementGrantsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_JohnsonAndJohnsonInnovationJJDCIncorporationMember" abstract="true" name="JohnsonAndJohnsonInnovationJJDCIncorporationMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_TechnologyLicenseCommitmentsMember" abstract="true" name="TechnologyLicenseCommitmentsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_CommercialNotesDueWithinNinetyDaysMember" abstract="true" name="CommercialNotesDueWithinNinetyDaysMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_CorporateHeadquartersInPasadenaMember" abstract="true" name="CorporateHeadquartersInPasadenaMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_TwoThousandsFourEquityIncentivePlanMember" abstract="true" name="TwoThousandsFourEquityIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_IncreaseDecreaseInCashAndInvestments" abstract="false" name="IncreaseDecreaseInCashAndInvestments" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_InitialTransactionPrice" abstract="false" name="InitialTransactionPrice" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_ResearchFacilityInMadisonMember" abstract="true" name="ResearchFacilityInMadisonMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_CommonStockPurchaseAgreementMember" abstract="true" name="CommonStockPurchaseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_OrganizationAndSignificantAccountingPoliciesTable" abstract="true" name="OrganizationAndSignificantAccountingPoliciesTable" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType"/>
  <xs:element id="arwr_CashEquivalentsGrossUnrealizedLosses" abstract="false" name="CashEquivalentsGrossUnrealizedLosses" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_UpfrontMilestonePaymentReceived" abstract="false" name="UpfrontMilestonePaymentReceived" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_VeronaTechnologyParkMember" abstract="true" name="VeronaTechnologyParkMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_LicenseAndCoFundingAgreementMember" abstract="true" name="LicenseAndCoFundingAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_AROXDHSupplyAgreementMember" abstract="true" name="AROXDHSupplyAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_EstimatedPaymentsForOperatingExpensesYearOne" abstract="false" name="EstimatedPaymentsForOperatingExpensesYearOne" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_AtTheMarketAgreementMember" abstract="true" name="AtTheMarketAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_CashEquivalentsHeldToMaturityAndMarketableSecuritiesAmortizedCost" abstract="false" name="CashEquivalentsHeldToMaturityAndMarketableSecuritiesAmortizedCost" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_HeldToMaturitySecuritiesFairValueNonCurrent" abstract="false" name="HeldToMaturitySecuritiesFairValueNonCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_AROHSDAgreementMember" abstract="true" name="AROHSDAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_LesseeOperatingLeaseLiabilityPaymentsDueYearFiveAndAfterYearFive" abstract="false" name="LesseeOperatingLeaseLiabilityPaymentsDueYearFiveAndAfterYearFive" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_ColoradoOwnerLLCMember" abstract="true" name="ColoradoOwnerLLCMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_LicenseCollaborationAndStockPurchaseAgreementMember" abstract="true" name="LicenseCollaborationAndStockPurchaseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_GrantDateFairValueOfOptionsGrantedDuringPeriod" abstract="false" name="GrantDateFairValueOfOptionsGrantedDuringPeriod" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_DevelopmentRegulatoryAndSalesMilestonesPayments" abstract="false" name="DevelopmentRegulatoryAndSalesMilestonesPayments" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_MilestonePaymentReceived" abstract="false" name="MilestonePaymentReceived" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_JNJ3989AROHBVAgreementMember" abstract="true" name="JNJ3989AROHBVAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_DrugManufacturingFacilityMember" abstract="true" name="DrugManufacturingFacilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_GlaxosmithklineIntellectualPropertyLimitedMember" abstract="true" name="GlaxosmithklineIntellectualPropertyLimitedMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_PercentageOfCommissionOnAggregateGrossProceedsFromSaleOfCommonStock" abstract="false" name="PercentageOfCommissionOnAggregateGrossProceedsFromSaleOfCommonStock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="arwr_CertificateOfDeposits" abstract="false" name="CertificateOfDeposits" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFour" abstract="false" name="FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_TwoThousandTwentyOneIncentivePlanMember" abstract="true" name="TwoThousandTwentyOneIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_FacilitiesMember" abstract="true" name="FacilitiesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_CashEquivalentsGrossUnrealizedGains" abstract="false" name="CashEquivalentsGrossUnrealizedGains" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_CommercialNotes" abstract="false" name="CommercialNotes" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_GrantDateFairValueOfOtherThanOptionsGrantedDuringPeriod" abstract="false" name="GrantDateFairValueOfOtherThanOptionsGrantedDuringPeriod" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_HalozymeIncMember" abstract="true" name="HalozymeIncMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_VisirnaTherapeuticsIncMember" abstract="true" name="VisirnaTherapeuticsIncMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_CashReceivableAsUpfrontPaymentDueUnderCollaborationAgreement" abstract="false" name="CashReceivableAsUpfrontPaymentDueUnderCollaborationAgreement" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_NumberOfAgreements" abstract="false" name="NumberOfAgreements" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="arwr_ComputersSoftwareOfficeEquipmentAndFurnitureGross" abstract="false" name="ComputersSoftwareOfficeEquipmentAndFurnitureGross" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_CashEquivalentsHeldToMaturityAndMarketableSecuritiesFairValue" abstract="false" name="CashEquivalentsHeldToMaturityAndMarketableSecuritiesFairValue" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_CollaborationAgreementMember" abstract="true" name="CollaborationAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_CertificateOfDepositDueWithinOneThroughTwoYearsMember" abstract="true" name="CertificateOfDepositDueWithinOneThroughTwoYearsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_MilestonePayments" abstract="false" name="MilestonePayments" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_CommercialNoteDueWithinOneYearMember" abstract="true" name="CommercialNoteDueWithinOneYearMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_ScheduleOfHeldToMaturitySecuritiesAndMarketableSecuritiesLineItems" abstract="true" name="ScheduleOfHeldToMaturitySecuritiesAndMarketableSecuritiesLineItems" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="arwr_OutsideOfEquityCompensationPlansMember" abstract="true" name="OutsideOfEquityCompensationPlansMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_HorizonTherapeuticsIrelandDACMember" abstract="true" name="HorizonTherapeuticsIrelandDACMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_JNJ75220795AROJNJ1Member" abstract="true" name="JNJ75220795AROJNJ1Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_TaxIncrementFinancingAward" abstract="false" name="TaxIncrementFinancingAward" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_AmountIntendsToInvestForBuildoutOfFacilities" abstract="false" name="AmountIntendsToInvestForBuildoutOfFacilities" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_CashEquivalentsHeldToMaturityAndMarketableSecuritiesGrossUnrealizedGains" abstract="false" name="CashEquivalentsHeldToMaturityAndMarketableSecuritiesGrossUnrealizedGains" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_MilestonePaymentEarned" abstract="false" name="MilestonePaymentEarned" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_OlpasiranAndAROAMG1AgreementMember" abstract="true" name="OlpasiranAndAROAMG1AgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_OrganizationAndSignificantAccountingPoliciesLineItems" abstract="true" name="OrganizationAndSignificantAccountingPoliciesLineItems" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="arwr_NumberOfDistinctPerformanceObligations" abstract="false" name="NumberOfDistinctPerformanceObligations" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="arwr_PaymentsOfLeaseholdImprovementsNetOfTenantImprovementAllowances" abstract="false" name="PaymentsOfLeaseholdImprovementsNetOfTenantImprovementAllowances" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_EquitySecuritiesFVNIAccumulatedGrossUnrealizedLossBeforeTax" abstract="false" name="EquitySecuritiesFVNIAccumulatedGrossUnrealizedLossBeforeTax" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_PercentageOfEligibleToReceiveTieredRoyaltiesOnNetSales" abstract="false" name="PercentageOfEligibleToReceiveTieredRoyaltiesOnNetSales" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="arwr_CommercialMilestonePaymentsAtFirstCommercialSale" abstract="false" name="CommercialMilestonePaymentsAtFirstCommercialSale" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_HeldToMaturitySecuritiesAndMarketableSecuritiesTableTableTextBlock" abstract="false" name="HeldToMaturitySecuritiesAndMarketableSecuritiesTableTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="arwr_NumberOfAcresOfLandPurchased" abstract="false" name="NumberOfAcresOfLandPurchased" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="arwr_JanssenPharmaceuticalsIncorporationMember" abstract="true" name="JanssenPharmaceuticalsIncorporationMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_AROXDHAgreementMember" abstract="true" name="AROXDHAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_MilestonePaymentReceivableUponAchievementOfPhaseTwoAndFirstPatientDosedInPhaseThree" abstract="false" name="MilestonePaymentReceivableUponAchievementOfPhaseTwoAndFirstPatientDosedInPhaseThree" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_ResearchEquipmentGross" abstract="false" name="ResearchEquipmentGross" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_ScheduleOfHeldToMaturitySecuritiesAndMarketableSecuritiesTable" abstract="true" name="ScheduleOfHeldToMaturitySecuritiesAndMarketableSecuritiesTable" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType"/>
  <xs:element id="arwr_SubleaseAgreementMember" abstract="true" name="SubleaseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_AdditionalRemainingDevelopmentRegulatoryAndSalesMilestonesPayments" abstract="false" name="AdditionalRemainingDevelopmentRegulatoryAndSalesMilestonesPayments" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_ResearchFacilityInSanDiegoMember" abstract="true" name="ResearchFacilityInSanDiegoMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_JanssenPharmaceuticalsAndJohnsonAndJohnsonInnovationJJDCIncorporationMember" abstract="true" name="JanssenPharmaceuticalsAndJohnsonAndJohnsonInnovationJJDCIncorporationMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_EquitySecuritiesFVNIAccumulatedGrossUnrealizedGainBeforeTax" abstract="false" name="EquitySecuritiesFVNIAccumulatedGrossUnrealizedGainBeforeTax" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_LicenseAgreementMember" abstract="true" name="LicenseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_CertificateOfDepositDueWithinOneYearMember" abstract="true" name="CertificateOfDepositDueWithinOneYearMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_AdditionalLandSubjectToLease" abstract="false" name="AdditionalLandSubjectToLease" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="arwr_NovartisMember" abstract="true" name="NovartisMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_CommercialNoteDueWithinOneThroughThreeYearsMember" abstract="true" name="CommercialNoteDueWithinOneThroughThreeYearsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_TakedaPharmaceuticalsUnitedStatesOfAmericaIncorporatedMember" abstract="true" name="TakedaPharmaceuticalsUnitedStatesOfAmericaIncorporatedMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_CashEquivalentsHeldToMaturityAndMarketableSecuritiesGrossUnrealizedLosses" abstract="false" name="CashEquivalentsHeldToMaturityAndMarketableSecuritiesGrossUnrealizedLosses" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_CommonStockCapitalSharesValueReservedForFutureIssuance" abstract="false" name="CommonStockCapitalSharesValueReservedForFutureIssuance" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_NumberOfDistinctBundle" abstract="false" name="NumberOfDistinctBundle" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="arwr_CollaborationAndLicenseAgreementMember" abstract="true" name="CollaborationAndLicenseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
