<SUBMISSION>
<ACCESSION-NUMBER>0001104659-13-009695
<TYPE>4/A
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20121231
<FILING-DATE>20130212
<DATE-OF-FILING-DATE-CHANGE>20130212
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>NICHOLS HOLLI
<CIK>0001221455
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4/A
<ACT>34
<FILE-NUMBER>001-34691
<FILM-NUMBER>13596909
</FILING-VALUES>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>ATLANTIC POWER CORP
<CIK>0001419242
<ASSIGNED-SIC>4900
<IRS-NUMBER>550886410
<STATE-OF-INCORPORATION>A1
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>ONE FEDERAL STREET
<STREET2>FLOOR 30
<CITY>BOSTON
<STATE>MA
<ZIP>02110
<PHONE>617-977-2400
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>ONE FEDERAL STREET
<STREET2>FLOOR 30
<CITY>BOSTON
<STATE>MA
<ZIP>02110
</MAIL-ADDRESS>
</ISSUER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>a4a.xml
<DESCRIPTION>4/A
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2012-12-31</periodOfReport>

    <dateOfOriginalSubmission>2013-01-03</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001419242</issuerCik>
        <issuerName>ATLANTIC POWER CORP</issuerName>
        <issuerTradingSymbol>AT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001221455</rptOwnerCik>
            <rptOwnerName>NICHOLS HOLLI</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ATLANTIC POWER CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>ONE FEDERAL STREET, 30TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02110</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Dividend Equivalent Rights</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2012-12-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>55</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>55</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6660</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Deferred Share Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2012-12-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1816</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>12.11</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1816</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>8476</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The dividend equivalent rights accrued on the deferred share units granted under the Company's Deferred Share Unit Plan, which provides for the payment of all accrued deferred share units and dividend equivalent rights to the reporting person following his or her termination as a director. Each deferred share unit and each dividend equivalent right is equal to the economic equivalent of one common share. The transactions reported in this Form 4 have been amended to reflect adjustments arising from the administration of the Company's Deferred Share Unit Plan.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Barry E. Welch, attorney-in-fact</signatureName>
        <signatureDate>2013-02-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
