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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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MIC-Info: RSA-MD5,RSA,
 B7zP1QUcbn75FtsgN848whwjgNXqjRMp8TA7dHUvgUANvgYIbNJHMZKW9Igk14yJ
 8GIRMI7fVuDKaTv1EQEF9A==

<SEC-DOCUMENT>0001179110-10-014621.txt : 20101004
<SEC-HEADER>0001179110-10-014621.hdr.sgml : 20101004
<ACCEPTANCE-DATETIME>20101004173637
ACCESSION NUMBER:		0001179110-10-014621
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20101001
FILED AS OF DATE:		20101004
DATE AS OF CHANGE:		20101004

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			OHara Kevin JP
		CENTRAL INDEX KEY:			0001299927

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-32722
		FILM NUMBER:		101106912

	MAIL ADDRESS:	
		STREET 1:		100 SOUTH WACKER DRIVE
		STREET 2:		SUITE 1800
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60606

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			INVESTMENT TECHNOLOGY GROUP INC
		CENTRAL INDEX KEY:			0000920424
		STANDARD INDUSTRIAL CLASSIFICATION:	SECURITY BROKERS, DEALERS & FLOTATION COMPANIES [6211]
		IRS NUMBER:				133757717
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		380 MADISON AVE
		STREET 2:		4TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10017
		BUSINESS PHONE:		2125884000

	MAIL ADDRESS:	
		STREET 1:		380 MADISON AVE
		STREET 2:		4TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10017
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-10-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000920424</issuerCik>
        <issuerName>INVESTMENT TECHNOLOGY GROUP INC</issuerName>
        <issuerTradingSymbol>ITG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001299927</rptOwnerCik>
            <rptOwnerName>OHara Kevin JP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>380 MADISON AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10017</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>
            </securityTitle>
            <transactionDate>
                <value>2010-10-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1050</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>14.29</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>16999</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Grant of deferred shares upon an elective deferral of cash fees, with the price equal to the fair market value of shares on the grant date, in a transaction exempt under Rule 16b-3(d).</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>P. Mats Goebels, by Power of Attorney filed with Form 3 dated January 17, 2007</signatureName>
        <signatureDate>2010-10-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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