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

    <schemaVersion>X0304</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2011-11-03</periodOfReport>

    <dateOfOriginalSubmission>2011-11-03</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000920427</issuerCik>
        <issuerName>UNITY BANCORP INC /NJ/</issuerName>
        <issuerTradingSymbol>unty</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001033204</rptOwnerCik>
            <rptOwnerName>DALLAS ROBERT H II</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O UNITY BANCORP INC</rptOwnerStreet1>
            <rptOwnerStreet2>64 OLD HIGHWAY 22</rptOwnerStreet2>
            <rptOwnerCity>CLINTON</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>08809</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Unity Bancorp Inc.</value>
            </securityTitle>
            <transactionDate>
                <value>2011-11-03</value>
            </transactionDate>
            <deemedExecutionDate>
                <value>2011-11-03</value>
            </deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>22155</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>6.4</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>22155</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>(1) (2)</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">(1) The reported securities are held by Dallas Holdings 2011 LLC.  A 49.9% interest in Dallas Financial Holdings II LLC was acquired by the Robert H. Dallas 1999 Exempt Testamentary Trust, a portion of the purchase price was allocated to the shares of UNTY, and valued them at market value.  The reporting person is the sole trustee of the Robert H. Dallas 1999 Exempt Testamentary Trust.</footnote>
        <footnote id="F2">This amended filing is to correct the signature of the reporting person.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Robert H Dallas II</signatureName>
        <signatureDate>2011-11-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
