<SEC-DOCUMENT>0001134710-17-000004.txt : 20170301
<SEC-HEADER>0001134710-17-000004.hdr.sgml : 20170301
<ACCEPTANCE-DATETIME>20170301183418
ACCESSION NUMBER:		0001134710-17-000004
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20170227
FILED AS OF DATE:		20170301
DATE AS OF CHANGE:		20170301

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:		7133506000

	MAIL ADDRESS:	
		STREET 1:		2800 POST OAK BLVD SUITE 2600
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77056-6175

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			GRINDSTAFF NICHOLAS M
		CENTRAL INDEX KEY:			0001134710

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-13831
		FILM NUMBER:		17656263

	MAIL ADDRESS:	
		STREET 1:		QUANTA SERVICES, INC.
		STREET 2:		2800 POST OAK BLVD., SUITE 2600
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77056-6175
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_148841124439833.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-02-27</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001134710</rptOwnerCik>
            <rptOwnerName>GRINDSTAFF NICHOLAS M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2800 POST OAK BLVD., SUITE 2600</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77056-6175</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>VP - Finance and Treasurer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-02-27</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>27000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>38.202</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>23659</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $38.18 to $38.23, inclusive. The reporting person undertakes to provide to Quanta Services, Inc., any security holder of Quanta Services, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Carolyn M. Campbell, Atty-in-Fact</signatureName>
        <signatureDate>2017-03-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
