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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2018-11-28</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001109546</issuerCik>
        <issuerName>PACIFIC MERCANTILE BANCORP</issuerName>
        <issuerTradingSymbol>PMBC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001561111</rptOwnerCik>
            <rptOwnerName>Deutsch James F.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O PATRIOT FINANCIAL PARTNERS III, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>CIRA CENTRE, 2929 ARCH STREET, 27TH FL</rptOwnerStreet2>
            <rptOwnerCity>PHILADELPHIA</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>19104</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>true</isOther>
            <officerTitle></officerTitle>
            <otherText>See Remarks (1)</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2169208.00</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Patriot Financial Partners III, L.P.</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Series A Non-Voting Preferred Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0.00</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                    <footnoteId id="F2"/>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1467155.00</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Patriot Financial Partners III, L.P.</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The securities are beneficially held by Patriot Financial Partners III, L.P. (the &quot;Patriot Fund&quot;). Patriot Financial Partners III, GP, L.P. (&quot;Patriot GP&quot;) is a general partner of Patriot Fund, and Patriot Financial Partners III, GP, LLC (&quot;Patriot LLC&quot;) is a general partner of Patriot GP. In addition, James F. Deutsch is a general partner of Patriot Fund and Patriot GP and a member of Patriot LLC. Accordingly, securities owned by Patriot Fund may be regarded as being beneficially owned by Patriot GP, Patriot LLC and James F. Deutsch. Mr. Deutsch disclaims beneficial ownership of the reported securities except to the extent of his pecuniary interest therein, and this report shall not be deemed an admission that he is a beneficial owner of such securities for the purposes of Section 16.</footnote>
        <footnote id="F2">The Series A Non-Voting Preferred Stock (&quot;Series A Preferred Stock&quot;) is automatically convertible into voting Common Stock upon any transfer of such Series A Preferred Stock to any person other than Patriot Fund or an affiliate of Patriot Fund (i) pursuant to any public offering or public sale of securities of the Issuer, (ii) in a transfer in which no transferee (or group of associated transferees) would receive 2% or more of any class of voting securities of the Issuer, or (iii) to a transferee that would control more than 50% of the voting securities of the Issuer without any transfer from Patriot Fund or any affiliate of Patriot Fund.</footnote>
    </footnotes>

    <remarks>In addition, Series A Preferred Stock is automatically convertible into a class of non-voting Common Stock to be created by the Issuer upon effectiveness of the Issuer's Amended and Restated Articles of Incorporation (the &quot;Amended Articles&quot;) establishing such class of non-voting Common Stock. Such non-voting Common Stock will have all of the rights and other attributes of the voting Common Stock, except that it will not be entitled to vote on any matter unless otherwise required by the California Corporations Code, and will convert into voting Common Stock subject to the same transfer restrictions applicable to the Series A Preferred Stock. The Issuer is expected to seek approval from its shareholders at the next annual meeting of shareholders (and at each annual shareholders meeting thereafter until approved).</remarks>

    <ownerSignature>
        <signatureName>/s/Curt A. Christianssen, attorney in fact for James F. Deutsch</signatureName>
        <signatureDate>2018-11-28</signatureDate>
    </ownerSignature>
</ownershipDocument>
