<SEC-DOCUMENT>0000866273-13-000050.txt : 20130829
<SEC-HEADER>0000866273-13-000050.hdr.sgml : 20130829
<ACCEPTANCE-DATETIME>20130829154101
ACCESSION NUMBER:		0000866273-13-000050
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20130827
FILED AS OF DATE:		20130829
DATE AS OF CHANGE:		20130829

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MATRIX SERVICE CO
		CENTRAL INDEX KEY:			0000866273
		STANDARD INDUSTRIAL CLASSIFICATION:	CONSTRUCTION SPECIAL TRADE CONTRACTORS [1700]
		IRS NUMBER:				731352174
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0630

	BUSINESS ADDRESS:	
		STREET 1:		5100 EAST SKELLY DRIVE
		STREET 2:		SUITE 700
		CITY:			TULSA
		STATE:			OK
		ZIP:			74135
		BUSINESS PHONE:		9188388822

	MAIL ADDRESS:	
		STREET 1:		5100 EAST SKELLY DRIVE
		STREET 2:		SUITE 700
		CITY:			TULSA
		STATE:			OK
		ZIP:			74135

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			LACKEY PAUL K
		CENTRAL INDEX KEY:			0001192252

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-15461
		FILM NUMBER:		131069065

	MAIL ADDRESS:	
		STREET 1:		NORDAM
		STREET 2:		11200 E. PINE
		CITY:			TULSA
		STATE:			OK
		ZIP:			74115
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_137780525143284.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-08-27</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000866273</issuerCik>
        <issuerName>MATRIX SERVICE CO</issuerName>
        <issuerTradingSymbol>MTRX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001192252</rptOwnerCik>
            <rptOwnerName>LACKEY PAUL K</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>5100 EAST SKELLY DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 700</rptOwnerStreet2>
            <rptOwnerCity>TULSA</rptOwnerCity>
            <rptOwnerState>OK</rptOwnerState>
            <rptOwnerZipCode>74135</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>COMMON STOCK</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2013-08-27</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>4700</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>34200</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">MATRIX SERVICE COMPANY COMMON STOCK.</footnote>
        <footnote id="F2">RESTRICTED STOCK UNIT - EACH UNIT WILL ENTITLE THE REPORTING PERSON TO ONE SHARE OF MATRIX SERVICE COMPANY COMMON STOCK IF AND WHEN THE CONDITIONS OF THE RESTRICTION HAVE BEEN SATISFIED.  FOR THIS GRANT, 100% WILL VEST ON THE THIRD ANNIVERSARY DATE.</footnote>
        <footnote id="F3">NOT APPLICABLE.</footnote>
        <footnote id="F4">INCLUDES 12,100 SHARES OF MATRIX SERVICE COMPANY COMMON STOCK OWNED OUTRIGHT.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Paul K. Lackey</signatureName>
        <signatureDate>2013-08-29</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
