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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 C4JXkNvuvVgoShiAVC0T/R0Gqmy9C+PUqd9QifnrWYdh6e9rkF0bU8g47qZAggBK
 JDuyFp9640r+K6RViyOJ9A==

<SEC-DOCUMENT>0001179110-05-023509.txt : 20051221
<SEC-HEADER>0001179110-05-023509.hdr.sgml : 20051221
<ACCEPTANCE-DATETIME>20051221114027
ACCESSION NUMBER:		0001179110-05-023509
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20051219
FILED AS OF DATE:		20051221
DATE AS OF CHANGE:		20051221

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MONTGOMERY SCOTT A
		CENTRAL INDEX KEY:			0001258734

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-13015
		FILM NUMBER:		051277438

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		310 282 6793

	MAIL ADDRESS:	
		STREET 1:		1840 CENTURY PARK EAST
		CITY:			LOS ANGELES
		STATE:			CA
		ZIP:			90067

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			NATIONAL MERCANTILE BANCORP
		CENTRAL INDEX KEY:			0000714801
		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
		IRS NUMBER:				953819685
		STATE OF INCORPORATION:			CA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1840 CENTURY PARK EAST
		CITY:			LOS ANGELES
		STATE:			CA
		ZIP:			90067
		BUSINESS PHONE:		3102772265

	MAIL ADDRESS:	
		STREET 1:		1840 CENTURY PARK EAST
		CITY:			LOS ANGELES
		STATE:			CA
		ZIP:			90067
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-12-19</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000714801</issuerCik>
        <issuerName>NATIONAL MERCANTILE BANCORP</issuerName>
        <issuerTradingSymbol>MBLA</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001258734</rptOwnerCik>
            <rptOwnerName>MONTGOMERY SCOTT A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1880 CENTURY PARK E STE. 800</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90067</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President/CEO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock NPV</value>
            </securityTitle>
            <transactionDate>
                <value>2005-12-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>21000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>18.8781</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>77288</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Family Trust</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">These shares were sold in a private transaction to the principal shareholders of the Company.</footnote>
        <footnote id="F2">For several years, Reporting Person has held all shares of Issuer's stock in his family trust. Reporting Person has indicated Indirect Ownership on this filing to properly report this form of ownership.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Scott A. Montgomery</signatureName>
        <signatureDate>2005-12-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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