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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2020-04-24</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000351834</issuerCik>
        <issuerName>SunOpta Inc.</issuerName>
        <issuerTradingSymbol>STKL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001687182</rptOwnerCik>
            <rptOwnerName>Oaktree Organics, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001499005</rptOwnerCik>
            <rptOwnerName>Oaktree Fund GP, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001402746</rptOwnerCik>
            <rptOwnerName>OAKTREE FUND GP I, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001403530</rptOwnerCik>
            <rptOwnerName>Oaktree Capital I, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001407178</rptOwnerCik>
            <rptOwnerName>OCM HOLDINGS I, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001407181</rptOwnerCik>
            <rptOwnerName>OAKTREE HOLDINGS, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001403528</rptOwnerCik>
            <rptOwnerName>Oaktree Capital Group, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001403525</rptOwnerCik>
            <rptOwnerName>Oaktree Capital Group Holdings GP, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001001085</rptOwnerCik>
            <rptOwnerName>BROOKFIELD ASSET MANAGEMENT INC.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001540229</rptOwnerCik>
            <rptOwnerName>Partners Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Special Shares, Series 2</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2020-04-24</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>0</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Series B-1 Preferred Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F5"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2020-04-24</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>12538.52</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1000.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F5"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F5"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>5015408</value>
                    <footnoteId id="F6"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12538.52</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Represents up to 6,000,0000 Special Shares, Series 2 (the &quot;Special Voting Shares&quot;) that, subject to certain caps (the &quot;Voting Trust Caps&quot;) as provided in the Voting Trust Agreement (as defined below), may be issued and deposited with OCM SunOpta Trustee LLC, an affiliate of the Reporting Persons (as defined below), as trustee (the &quot;Trustee&quot;) for and on behalf of Oaktree Organics, LP. (&quot;Organics&quot;) and other holders of Preferred Shares (as defined below) of SunOpta Foods Inc. (the &quot;Subsidiary&quot;) from time to time pursuant to a voting trust agreement dated April 24, 2020 (the &quot;Voting Trust Agreement&quot;), among SunOpta Inc. (the &quot;Company&quot;), the Subsidiary, Organics, Oaktree Huntington Investment Fund II, L.P. and the Trustee. The Special Shares serve as the mechanism for attaching exchanged voting to the Preferred Shares. As a result of the Voting Trust Caps, no Special Voting Shares have been issued to the Reporting Persons (as defined below).</footnote>
        <footnote id="F2">Organics directly owns the securities reported herein. This Form 4 is also being filed by (i) Oaktree Fund GP, LLC (&quot;Fund GP&quot;) in its capacity as general partner of Organics (ii) Oaktree Fund GP I, L.P. (&quot;GP I&quot;) in its capacity as managing member of Fund GP; (iii) Oaktree Capital I, L.P. (&quot;Capital I&quot;) in its capacity as the general partner of GP I; (iv) OCM Holdings I, LLC (&quot;Holdings I&quot;) in its capacity as the general partner of Capital I; (v) Oaktree Holdings, LLC (&quot;Holdings LLC&quot;) in its capacity as the managing member of Holdings I;. (vi) Oaktree Capital Group, LLC (&quot;OCG&quot;) in its capacity as the managing member of Holdings LLC; (vii) Oaktree Capital Group Holdings GP, LLC (&quot;OCGH GP&quot;) in its capacity as the duly appointed manager of OCG;</footnote>
        <footnote id="F3">(Continued from footnote 2) (viii) Brookfield Asset Management, Inc. (&quot;BAM&quot;) in its capacity as the indirect owner of the class A units of OCG and (ix) Partners Limited, in its capacity as the sole owner of Class B Limited Voting Shares of BAM (each a &quot;Reporting Person&quot; and, collectively, the &quot;Reporting Persons&quot;).</footnote>
        <footnote id="F4">Each Reporting Person disclaims beneficial ownership of all equity securities reported herein except to the extent of its respective pecuniary interest therein, and the filing of this Form 4 shall not be construed as an admission that any such Reporting Person is the beneficial owner of any equity securities covered by this Form 4.</footnote>
        <footnote id="F5">Shares of the Series B-1 Preferred Stock of the Subsidiary (the &quot;Preferred Shares&quot;) may be exchanged at any time into the number of Common Shares of the Company, subject to certain restrictions including those set forth in Note (6) below, equal to, per Preferred Share, the quotient of the liquidation preference of the Preferred Share divided by $2.50 (the &quot;Exchange Price&quot;), subject to customary anti-dilution adjustments, provided that the Exchange Price may not be lower than $2.00 (subject to adjustment in certain circumstances). The Preferred Shares have no expiration date.</footnote>
        <footnote id="F6">The number of Common Shares reported herein represents the number of Common Shares that would be issuable upon the exchange of all of the 12,538.52 Preferred Shares held by Organics without giving effect to the Exchange Caps and the Rights Plan Exchange Cap (each as defined in the Subsidiary's Second Amended and Restated Certificate of Incorporation). The Exchange Caps and the Rights Plan Exchange Cap limit the number Common Shares that are exchangeable by the Reporting Persons for the Preferred Shares.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>OAKTREE ORGANICS, L.P. By: Oaktree Fund GP, LLC Its: GP, By: Oaktree Fund GP I, L.P. Its: Managing Member By: /s/ Ting He, Authorized Signatory</signatureName>
        <signatureDate>2020-04-28</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>OAKTREE FUND GP, LLC By: Oaktree Fund GP I, L.P. Its: Managing Member By: /s/ Ting He, Authorized Signatory</signatureName>
        <signatureDate>2020-04-28</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>OAKTREE FUND GP I, L.P. By: /s/ Ting He, Authorized Signatory</signatureName>
        <signatureDate>2020-04-28</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>OAKTREE CAPITAL I, L.P. By: /s/ Ting He, Vice President</signatureName>
        <signatureDate>2020-04-28</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>OCM HOLDINGS I, LLC By: /s/ Ting He, Vice President</signatureName>
        <signatureDate>2020-04-28</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>OAKTREE HOLDINGS, LLC By: /s/ Ting He, Vice President</signatureName>
        <signatureDate>2020-04-28</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>OAKTREE CAPITAL GROUP, LLC By: Oaktree Capital Group Holdings GP, LLC Its: Manager By: /s/ Ting He, Vice President</signatureName>
        <signatureDate>2020-04-28</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>OAKTREE CAPITAL GROUP HOLDINGS GP, LLC By: /s/ Ting He, Vice President</signatureName>
        <signatureDate>2020-04-28</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>BROOKFIELD ASSET MANAGEMENT INC. By: /s/ Jessica Diab, Vice President, Legal &amp; Regulatory</signatureName>
        <signatureDate>2020-04-28</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>PARTNERS LIMITED By: /s/ Brian Lawson, President</signatureName>
        <signatureDate>2020-04-28</signatureDate>
    </ownerSignature>
</ownershipDocument>
