<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2020-04-09</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000010048</issuerCik>
        <issuerName>BARNWELL INDUSTRIES INC</issuerName>
        <issuerTradingSymbol>BRN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001484439</rptOwnerCik>
            <rptOwnerName>Tirpak Bradley M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>39 DOVER STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LONDON</rptOwnerCity>
            <rptOwnerState>X0</rptOwnerState>
            <rptOwnerZipCode>W1S 3NN</rptOwnerZipCode>
            <rptOwnerStateDescription>UNITED KINGDOM</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <officerTitle></officerTitle>
            <otherText>13(d) GROUP MEMBER</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>34127</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The Reporting Person directly beneficially owns 34,127 shares of Common Stock.  The Reporting Person is a member of a Section 13(d) group (within the meaning of Section 13(d) of the Exchange Act) that beneficially owns in the aggregate more than 10% of the Issuer's outstanding shares of Common Stock as disclosed in a Schedule 13D/A, filed on behalf of the Reporting Person and certain other stockholders of the Issuer on April 10, 2020.  The securities reported herein do not include any securities held by any group member other than the Reporting Person, as such securities have been reported in separate Form 3 and Form 4 filings by such other group members.</footnote>
    </footnotes>

    <remarks>The election of the Reporting Person as a Director became effective on April 9, 2020 when the independent inspector of election delivered his certified final report setting forth the results of the 2020 Annual Meeting of Stockholders of Barnwell Industries, Inc., which was held on April 3, 2020.</remarks>

    <ownerSignature>
        <signatureName>/s/ Bradley M. Tirpak</signatureName>
        <signatureDate>2020-04-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
