<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-11-24</periodOfReport>
    <issuer>
        <issuerCik>0000934549</issuerCik>
        <issuerName>ACACIA RESEARCH CORP</issuerName>
        <issuerTradingSymbol>ACTG/CBMX</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001189618</rptOwnerCik>
            <rptOwnerName>HAYNES CLAYTON J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>500 NEWPORT CENTER DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2>7TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEWPORT BEACH</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92660</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>CFO, Treas. Sr. V.P. Finance</officerTitle></reportingOwnerRelationship></reportingOwner><derivativeTable><derivativeTransaction><securityTitle><value>Stock Option (Right to Buy)</value></securityTitle><conversionOrExercisePrice><value>5.17</value></conversionOrExercisePrice><transactionDate><value>2003-11-24</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>37620</value></transactionShares><transactionPricePerShare><value>0</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><footnoteId id="F1"/></exerciseDate><expirationDate><value>2013-11-24</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Acacia Research-Acacia Technologies Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>37620</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>169450</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes><footnote id="F1">The option shares are exercisable in twelve equal monthly installments upon Optionee's completion of each month of service measured from 1/2/06.</footnote></footnotes><remarks/><ownerSignature><signatureName>Clayton J. Haynes</signatureName><signatureDate>2003-11-24</signatureDate></ownerSignature></ownershipDocument>

