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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-10-19</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000089270</issuerCik>
        <issuerName>SL INDUSTRIES INC</issuerName>
        <issuerTradingSymbol>SLI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001208889</rptOwnerCik>
            <rptOwnerName>SCHWARZ MARK E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CRESCENT COURT</rptOwnerStreet1>
            <rptOwnerStreet2>STE 1400</rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75201</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-10-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>183366</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>14.5</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>see explanation</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Pursuant to a modified &quot;dutch auction&quot; tender offer by the Issuer, NP and NFF (each as defined below) tendered, and the Issuer accepted for payment, the shares of Common Stock reflected hereon.</footnote>
        <footnote id="F2">The Reporting Person is a director of the Issuer.  Newcastle Partners, L.P. (&quot;NP&quot;) and Newcastle Focus Fund II, L.P. (&quot;NFF&quot;) directly owned shares of the Issurer's Common Stock. The Reporting Person is the managing member of NCG. Accordingly, the Reporting Person may be deemed to have beneficially owned the shares of the Issuer's Common Stock directly owned by NP and NFF. The Reporting Person disclaims beneficial ownership of the shares of the Issuer's Common stock owned by NP and NFF except to the extent of his pecuniary interest therein.  The Reporting Person continues to directly own 26,123 vested stock options exercisable into the Common Stock.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Mark E Schwarz</signatureName>
        <signatureDate>2010-10-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
