<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0203</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2010-12-14</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001492691</issuerCik>
        <issuerName>SWIFT TRANSPORTATION CO</issuerName>
        <issuerTradingSymbol>SWFT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001506839</rptOwnerCik>
            <rptOwnerName>Henkels Virginia</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>SWIFT TRANSPORTATION COMPANY</rptOwnerStreet1>
            <rptOwnerStreet2>2200 SOUTH 75TH AVENUE</rptOwnerStreet2>
            <rptOwnerCity>PHOENIX</rptOwnerCity>
            <rptOwnerState>AZ</rptOwnerState>
            <rptOwnerZipCode>85043</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Exec VP, CFO, &amp; Treasurer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (Right-To-Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>15.63</value>
                <footnoteId id="F4"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2017-10-16</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Class A Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>20000</value>
                    <footnoteId id="F4"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (Right-To-Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>16.79</value>
                <footnoteId id="F4"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2018-08-27</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Class A Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>100000</value>
                    <footnoteId id="F4"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (Right-To-Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>8.80</value>
                <footnoteId id="F4"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2020-02-28</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Class A Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>24000</value>
                    <footnoteId id="F4"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Subject to certain acceleration, forfeiture, and termination provisions and the closing of the Issuer's initial public offering, the options vested as to 6,666 shares on October 16, 2010, and vest as to an additional 6,667 shares on each of October 16, 2011 and October 16, 2012.  Upon exercise, the options convert to the Issuer's Class A common stock on a one-to-one basis.</footnote>
        <footnote id="F2">Subject to certain acceleration, forfeiture, and termination provisions and the closing of the Issuer's initial public offering, the options vest as to 33,333 shares on each of August 27, 2011, and August 27, 2012, and the remaining 33,334 shares on August 27, 2013.  Upon exercise, the options convert to the Issuer's Class A common stock on a one-to-one basis.</footnote>
        <footnote id="F3">Subject to certain acceleration, forfeiture, and termination provisions and the closing of the Issuer's initial public offering, the options vest as to 8,000 shares on each of February 28, 2013, February 28, 2014, and February 28, 2015. Upon exercise, the options convert to the Issuer's Class A common stock on a one-to-one basis.</footnote>
        <footnote id="F4">Reflects a four-for-five reverse stock split effected on November 29, 2010, in connection with the Issuer's initial public offering.</footnote>
    </footnotes>

    <remarks>No non-derivative securities are beneficially owned.</remarks>

    <ownerSignature>
        <signatureName>/s/ Virginia Henkels, by James Fry, attorney-in-fact, pursuant to a POA filed herewith</signatureName>
        <signatureDate>2010-12-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
