<SUBMISSION>
<ACCESSION-NUMBER>0001179110-16-016867
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20151231
<FILING-DATE>20160104
<DATE-OF-FILING-DATE-CHANGE>20160104
<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>3 ALLIED DRIVE
<STREET2>SUITE 220
<CITY>DEDHAM
<STATE>MA
<ZIP>02026
<PHONE>617-977-2400
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>3 ALLIED DRIVE
<STREET2>SUITE 220
<CITY>DEDHAM
<STATE>MA
<ZIP>02026
</MAIL-ADDRESS>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>McNeil John Alexander
<CIK>0001489397
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-34691
<FILM-NUMBER>161317368
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>200 CLARENDON STREET
<CITY>BOSTON
<STATE>MA
<ZIP>02116
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-12-31</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001489397</rptOwnerCik>
            <rptOwnerName>McNeil John Alexander</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ATLANTIC POWER CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>3 ALLIED DRIVE, SUITE 220</rptOwnerStreet2>
            <rptOwnerCity>DEDHAM</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02026</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 shares</value>
            </securityTitle>
            <transactionDate>
                <value>2015-12-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1.99</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>56500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>6.00% Convertible Debentures due December 31, 2019</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>10.48</value>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2015-12-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionTotalValue>
                    <value>36125</value>
                    <footnoteId id="F6"/>
                </transactionTotalValue>
                <transactionPricePerShare>
                    <value>55.99</value>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2015-12-31</value>
            </exerciseDate>
            <expirationDate>
                <value>2019-12-31</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>3448</value>
                    <footnoteId id="F3"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>72250</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>6.25% Convertible Debentures due March 15, 2017</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>9.39</value>
                <footnoteId id="F7"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2015-12-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionTotalValue>
                    <value>72250</value>
                    <footnoteId id="F11"/>
                </transactionTotalValue>
                <transactionPricePerShare>
                    <value>64.3</value>
                    <footnoteId id="F9"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2015-12-31</value>
            </exerciseDate>
            <expirationDate>
                <value>2017-03-15</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>7692</value>
                    <footnoteId id="F8"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>151725</value>
                    <footnoteId id="F10"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Deferred share units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F12"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2015-12-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>8872</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1.69</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F12"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F12"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>8872</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>34645</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The common shares were acquired at a price of Cdn$2.74 which was converted to the U.S. dollar equivalent of $1.99 using the December 31, 2015 end of day exchange rate of .7225.</footnote>
        <footnote id="F2">The 6.00% Convertible Debentures due December 31, 2019 are convertible into approximately 68.9655 common shares per Cdn$1,000 principal amount, at any time, at the option of the holder representing a conversion price of Cdn$14.50 per common share. The conversion price of Cdn$14.50 was converted to the U.S. dollar equivalent of $10.48 using the December 31, 2015 end of day exchange rate of .7225.</footnote>
        <footnote id="F3">The 6.00% Convertible Debentures due December 31, 2019 are convertible into approximately 68.9655 common shares per Cdn$1,000 principal amount, at any time, at the option of the holder representing a conversion price of Cdn$14.50 per common share. The Cdn$50,000 of convertible debentures converts to 3,448 common shares using the December 31, 2015 end of day exchange rate of .7225.</footnote>
        <footnote id="F4">The Cdn$50,000 principal of 6.00% Convertible Debentures due December 31, 2019 were purchased at a price of Cdn$77.50. This was converted to a U.S. dollar equivalent of $55.99 using the December 31, 2015 end of day exchange rate of .7225.</footnote>
        <footnote id="F5">The Cdn$100,000 principal of 6.00% Convertible Debentures due December 31, 2019 were converted to a U.S. dollar equivalent of $72,250 using the December 31, 2015 end of day exchange rate of .7225.</footnote>
        <footnote id="F6">The Cdn$50,000 principal of 6.00% Convertible Debentures due December 31, 2019 were converted to a U.S. dollar equivalent of $36,125 using the December 31, 2015 end of day exchange rate of .7225.</footnote>
        <footnote id="F7">The 6.25% Convertible Debentures due March 15, 2017 are convertible into approximately 76.9231 common shares per Cdn$1,000 principal amount, at any time, at the option of the holder representing a conversion price of Cdn$13.00 per common share. The conversion price of Cdn$13.00 was converted to the U.S. dollar equivalent of $9.39 using the December 31, 2015 end of day exchange rate of .7225.</footnote>
        <footnote id="F8">The 6.25% Convertible Debentures due March 15, 2017 are convertible into approximately 76.9231 common shares per Cdn$1,000 principal amount, at any time, at the option of the holder representing a conversion price of Cdn$13.00 per common share. The Cdn$100,000 of convertible debentures converts to 7,692 common shares using the December 31, 2015 end of day exchange rate of .7225.</footnote>
        <footnote id="F9">The Cdn$100,000 principal of 6.25% Convertible Debentures due March 15, 2017 were purchased at a price of Cdn$89.00. This was converted to a U.S. dollar equivalent of $64.30 using the December 31, 2015 end of day exchange rate of .7225.</footnote>
        <footnote id="F10">The Cdn$210,000 principal of 6.25% Convertible Debentures due March 15, 2017 were converted to a U.S. dollar equivalent of $151,725 using the December 31, 2015 end of day exchange rate of .7225.</footnote>
        <footnote id="F11">The Cdn$100,000 principal of 6.25% Convertible Debentures due March 15, 2017 were converted to a U.S. dollar equivalent of $72,250 using the December 31, 2015 end of day exchange rate of .7225.</footnote>
        <footnote id="F12">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.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s John S. Miele, attorney-in-fact</signatureName>
        <signatureDate>2016-01-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
