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

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2007-01-01</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000914713</issuerCik>
        <issuerName>MILLS CORP</issuerName>
        <issuerTradingSymbol>MLS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001384996</rptOwnerCik>
            <rptOwnerName>MacMahon Douglas M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O FARALLON CAPITAL MANAGEMENT, L.L.C.,</rptOwnerStreet1>
            <rptOwnerStreet2>ONE MARITIME PLAZA, SUITE 1325</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94111</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <officerTitle></officerTitle>
            <otherText>Member of Group Owning 10%</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6145000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnotes</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The amount of securities shown in this row is owned directly by Farallon Capital Partners, L.P., Farallon Capital Institutional Partners, L.P., Farallon Capital Institutional Partners II, L.P., Farallon Capital Institutional Partners III, L.P. and Tinicum Partners, L.P. (collectively, the &quot;Partnerships&quot;).  As the general partner to each of the Partnerships, Farallon Partners, L.L.C. (&quot;FPLLC&quot;) may be deemed to be the beneficial owner of the Issuer's securities held by each of the Partnerships.</footnote>
        <footnote id="F2">Effective as of January 1, 2007, Douglas M. MacMahon (&quot;MacMahon&quot;) became a managing member of FPLLC, and as a result MacMahon may be deemed to be the beneficial owner of the Issuer's securities held by the Partnerships.</footnote>
        <footnote id="F3">All of such securities of the Issuer have been previously reported by the Partnerships and other related entities and individuals on the Form 3s filed on August 28, 2006 by the Partnerships and other related entities and individuals listed on such forms.  There have been no transactions in such securities by the Partnerships or individuals since such forms were filed.</footnote>
        <footnote id="F4">MacMahon and the individuals identified in the prior Form 3s disclaim any beneficial ownership of any of the Issuer's securities reported or referred to herein for purposes of Rules 16a-1(a) under the Securities Exchange Act of 1934, as amended (the &quot;'34 Act&quot;).  FPLLC disclaims any beneficial ownership of any of the Issuer's securities reported or referred to herein for purposes of Rule 16a-1(a) under the '34 Act, or otherwise, except as to securities representing FPLLC's pro rata interest in, and interest in the profits of, the Partnerships.</footnote>
        <footnote id="F5">MacMahon, together with the entities identified in footnote (1) of this Form 3 and the individuals identified in the prior Form 3s, may be deemed members of a group holding equity securities of the Issuer.  The filing of this Form 3 shall not be deemed to be an admission that such entities and individuals are members of such group.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Mark C. Wehrly, as attorney-in-fact for Douglas M. MacMahon</signatureName>
        <signatureDate>2007-01-08</signatureDate>
    </ownerSignature>
</ownershipDocument>
