<SEC-DOCUMENT>0001140361-17-025730.txt : 20170621
<SEC-HEADER>0001140361-17-025730.hdr.sgml : 20170621
<ACCEPTANCE-DATETIME>20170621183910
ACCESSION NUMBER:		0001140361-17-025730
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20170621
FILED AS OF DATE:		20170621
DATE AS OF CHANGE:		20170621

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			UNITED SECURITY BANCSHARES
		CENTRAL INDEX KEY:			0001137547
		STANDARD INDUSTRIAL CLASSIFICATION:	NATIONAL COMMERCIAL BANKS [6021]
		IRS NUMBER:				912112732
		STATE OF INCORPORATION:			CA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		2126 INYO STREET
		CITY:			FRESNO
		STATE:			CA
		ZIP:			93721
		BUSINESS PHONE:		5592484930

	MAIL ADDRESS:	
		STREET 1:		2126 INYO STREET
		CITY:			FRESNO
		STATE:			CA
		ZIP:			93721

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			WOODS DENNIS R
		CENTRAL INDEX KEY:			0001144507
		STATE OF INCORPORATION:			CA
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-32897
		FILM NUMBER:		17923730

	MAIL ADDRESS:	
		STREET 1:		1525 E. SHAW AVE.
		CITY:			FRESNO
		STATE:			CA
		ZIP:			93710
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-06-21</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001137547</issuerCik>
        <issuerName>UNITED SECURITY BANCSHARES</issuerName>
        <issuerTradingSymbol>UBFO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001144507</rptOwnerCik>
            <rptOwnerName>WOODS DENNIS R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2126 INYO STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>FRESNO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>93721</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CEO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>UBFO COMMON STOCK</value>
            </securityTitle>
            <transactionDate>
                <value>2017-06-21</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>26680</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>9.70</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1101862</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">These shares were held as custodian under the California Uniform Transfers to Minors Act.  The beneficiary has reached the age of legal majority and the reporting person has transferred the shares to or for the benefit of the beneficiary.</footnote>
        <footnote id="F2">INCLUDES 10,126 SHARES AS CUSTODIAN FOR MINORS &amp; 33,838 SHARES OWNED BY SPOUSE.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/S/ DENNIS R WOODS</signatureName>
        <signatureDate>2017-06-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
