<SEC-DOCUMENT>0001050915-19-000031.txt : 20190311
<SEC-HEADER>0001050915-19-000031.hdr.sgml : 20190311
<ACCEPTANCE-DATETIME>20190311183535
ACCESSION NUMBER:		0001050915-19-000031
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20190308
FILED AS OF DATE:		20190311
DATE AS OF CHANGE:		20190311

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Gregory Paul Craig
		CENTRAL INDEX KEY:			0001694207

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-13831
		FILM NUMBER:		19673474

	MAIL ADDRESS:	
		STREET 1:		607 HUNTERS GROVE
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77024

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			QUANTA SERVICES INC
		CENTRAL INDEX KEY:			0001050915
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRICAL WORK [1731]
		IRS NUMBER:				742851603
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		2800 POST OAK BLVD
		STREET 2:		SUITE 2600
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77056-6175
		BUSINESS PHONE:		713-629-7600

	MAIL ADDRESS:	
		STREET 1:		2800 POST OAK BLVD SUITE 2600
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77056-6175
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_155234372114464.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-03-08</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001050915</issuerCik>
        <issuerName>QUANTA SERVICES INC</issuerName>
        <issuerTradingSymbol>PWR</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001694207</rptOwnerCik>
            <rptOwnerName>Gregory Paul Craig</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2800 POST OAK BLVD.</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 2600</rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77056</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CSO &amp; President-Pipeline&amp;Ind</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-03-08</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>33417</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>180038</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">These shares represent restricted stock units that may be settled solely by the issuance of an equal number of shares of common stock of the Company and remain subject to vesting based on the passage of time and continued employment.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Matthew D. McCoy, Atty-in-Fact</signatureName>
        <signatureDate>2019-03-11</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
