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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-04-05</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>2010-04-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>13139</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>217056</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>see explanation</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Transaction constitutes a distribution of shares to withdrawing partners of NP as of March 31, 2010.</footnote>
        <footnote id="F2">The Reporting Person is a director of the Issuer.  Newcastle Partners, LP directly owns shares of the Issurer's Common Stock.  Newcastle Capital Management, LP is the general partner of Newcastle Partners, LP. Newcastle Capital Group, LLC is the general partner of Newcastle Capital Management, LP. The Reporting Person is the managing member of Newcastle Capital Group, LLC.

Accordingly, the Reporting Person may be deemed to beneficially own the shares of the Issuer's Common Stock directly owned by Newcastle Partners, L.P. The Reporting Person disclaims beneficial ownership of the shares of the Issuer's Common stock owned by Newcastle Partners, L.P. except to the extent of his pecuniary interest therein.</footnote>
        <footnote id="F3">Includes, as of 4/5/2010 after giving effect to the transaction reported herein, (1) 190,933 shares of the Issuer's Common Stock owned by NP and (2) 26,123 vested options exercisable into shares of the Issuer's Common Stock owned by the Reporting Person.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Mark E. Schwarz</signatureName>
        <signatureDate>2010-04-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
