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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-09-30</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001401523</rptOwnerCik>
            <rptOwnerName>Pound Gregory J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>TRANSMONTAIGNE</rptOwnerStreet1>
            <rptOwnerStreet2>200 MANSELL COURT, E., SUITE 600</rptOwnerStreet2>
            <rptOwnerCity>ROSWELL</rptOwnerCity>
            <rptOwnerState>GA</rptOwnerState>
            <rptOwnerZipCode>30076-4853</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>President, COO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Units Representing Limited Partner Interest</value>
            </securityTitle>
            <transactionDate>
                <value>2009-09-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>19584</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>29979</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Units Representing Limited Partner Interest</value>
            </securityTitle>
            <transactionDate>
                <value>2009-09-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>8257</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>26.90</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>21722</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2009-09-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>19584.59</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Units Representing Limited Partner Interest</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>19584.59</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Represents the settlement of phantom units granted under the Amended and Restated Savings and Retention Plan (the &quot;Plan&quot;).  Pursuant to applicable SEC reporting requirements, the settlement of the phantom units in exchange for common units of TLP is reported on this Form 4 as a disposition of the phantom units being settled and a simultaneous acquisition of the underlying common units.</footnote>
        <footnote id="F2">Each phantom unit represents the right to receive one common unit of TLP, or the cash value thereof.  In lieu of issuing fractional common units, the Plan Administrator settled fractional phantom units for cash based on the closing price of the common units on the New York Stock Exchange on the settlement date, September 30, 2009.</footnote>
        <footnote id="F3">The Reporting Person continues to serve as an executive officer and employee however the Reporting Person has satisfied the age and length of service thresholds under the Plan and therefore 100% of his phantom units vested on September 1, 2009. On September 30, 2009, the Plan Administrator determined to settle the Reporting Person's phantom units by the issuance of common units which the Reporting Person is treating as the &quot;settlement date&quot; for the purposes of this Report. Pursuant to applicable SEC reporting requirements, the settlement of the phantom units in exchange for common units of TLP is reported on this Form 4 as a disposition of the phantom units being settled and a simultaneous acquisition of the underlying common units. See Table I and note 2 above.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Gregory J. Pound</signatureName>
        <signatureDate>2009-10-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
