-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 PB05uc8d47XakDPZFNXjczpSe+PxsvM+v2roiPe/9xQ4DX9HDovVMlleeFDuOCdG
 Py71fp1YJ+6ioCMLQU8ekw==

<SEC-DOCUMENT>0001140361-10-000108.txt : 20100104
<SEC-HEADER>0001140361-10-000108.hdr.sgml : 20100101
<ACCEPTANCE-DATETIME>20100104141523
ACCESSION NUMBER:		0001140361-10-000108
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20091231
FILED AS OF DATE:		20100104
DATE AS OF CHANGE:		20100104

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			JENKINS-STARK JACK
		CENTRAL INDEX KEY:			0001208353

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-26091
		FILM NUMBER:		10501432

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			TC PIPELINES LP
		CENTRAL INDEX KEY:			0001075607
		STANDARD INDUSTRIAL CLASSIFICATION:	NATURAL GAS TRANSMISSION [4922]
		IRS NUMBER:				522135448
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		13710 FNB PARKWAY
		CITY:			OMAHA
		STATE:			NE
		ZIP:			68154-5200
		BUSINESS PHONE:		8772902772

	MAIL ADDRESS:	
		STREET 1:		13710 FNB PARKWAY
		CITY:			OMAHA
		STATE:			NE
		ZIP:			68154-5200
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-12-31</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001075607</issuerCik>
        <issuerName>TC PIPELINES LP</issuerName>
        <issuerTradingSymbol>TCLP</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001208353</rptOwnerCik>
            <rptOwnerName>JENKINS-STARK JACK</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>13710 FNB PARKWAY</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>OMAHA</rptOwnerCity>
            <rptOwnerState>NE</rptOwnerState>
            <rptOwnerZipCode>68154-5200</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Deferred Share Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2009-12-31</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>203</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common units representing limited p/ship interests</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>203</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4264</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">N/A - Upon termination of board service, Common Units representing limited partnership interests may be purchased on the open market on behalf of Mr. Jenkins-Stark whereby he would receive Common Units in a number equal to the number of Deferred Share Units (&quot;DSUs&quot;) recorded in his account less any applicable withholdings. Alternatively, Mr.Jenkins-Stark may elect to receive the value of his DSU entitlement in cash.  The cash payment amount shall be determined by multiplying the number of DSUs recorded in his account by the Fair Market Value of a Common Unit less any applicable withholdings.</footnote>
        <footnote id="F2">N/A - the DSUs are fully vested and are redeemable only following Mr. Jenkins-Stark's termination of Board service.</footnote>
        <footnote id="F3">Mr. Jenkins-Stark elected to have a portion (50%) of his annual retainer paid in the form of DSUs in lieu of cash.  The number of DSUs is calculated based on the Fair Market Value of the Common Units representing limited partnership interests.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Tara E. Shaw, Attorney for Jack Jenkins-Stark</signatureName>
        <signatureDate>2010-01-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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