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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-02-29</periodOfReport>

    <issuer>
        <issuerCik>0001319229</issuerCik>
        <issuerName>TransMontaigne Partners L.P.</issuerName>
        <issuerTradingSymbol>TLP</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001422494</rptOwnerCik>
            <rptOwnerName>Davis Deborah A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>TRANSMONTAIGNE</rptOwnerStreet1>
            <rptOwnerStreet2>1670 BROADWAY, SUITE 3100</rptOwnerStreet2>
            <rptOwnerCity>DENVER</rptOwnerCity>
            <rptOwnerState>CO</rptOwnerState>
            <rptOwnerZipCode>80202</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>SVP, Chief Accounting Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2008-02-29</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2536.35</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Unit representing limited partner interest</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2536.35</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5265.31</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F3">The awards granted under the Plan were ratified by the Board of Directors of TransMontaigne Inc. on February 15, 2008.  The awards may be allocated to and deemed invested in the various investment funds available under the Plan, one of which tracks the financial performance of the TLP common units (the &quot;TLP Index Fund&quot;).  The awards were allocated among the investment funds available under the Plan, including the TLP Index Fund, after the close of the market on February 29, 2008.</footnote>
        <footnote id="F1">Each phantom unit represents the right to receive one common unit of TLP, or the cash value thereof.</footnote>
        <footnote id="F2">Phantom units will vest 50% on January 1, 2010 and 50% on January 1, 2011, but are subject to earlier vesting upon achieving certain age or service thresholds as defined in the Amended and Restated Savings and Retention Plan (the &quot;Plan&quot;) adopted by the Board of Directors of TransMontaigne Inc., effective as of January 1, 2008.  Upon vesting, phantom units may be paid out, in the sole discretion of the Plan administrator, in cash or in common units of TLP, or a combination thereof, in an amount equal to the value of the vested portion of a reporting person's account.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>DeborahA.Davis</signatureName>
        <signatureDate>2008-03-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
