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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2016-10-07</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <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>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Special Shares, Series 1</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>9492800</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnotes</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Series A Preferred Stock</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>9492800</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The Special Shares, Series 1 (the &quot;Special Voting Shares&quot;) were issued to and deposited with an affiliate of the Reporting Persons (as defined below), as trustee (the &quot;Trustee&quot;) for and on behalf of Oaktree Organics, L.P. (&quot;Organics&quot;) and other holders of Series A Preferred Shares of SunOpta Foods Inc. (the &quot;Subsidiary&quot;) from time to time pursuant to a voting trust agreement dated October 7, 2016 (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 number of Special Voting Shares represents the number of Common Shares exchangeable for the Preferred Shares (as defined below), subject to certain adjustments and restrictions.</footnote>
        <footnote id="F2">The Series A 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, equal to, per Preferred Share, the quotient of the liquidation preference of the Preferred Share divided by $7.50 (the &quot;Exchange Price&quot;), subject to customary anti-dilution adjustments, provided that the Exchange Price may not be lower than $7.00 (subject to adjustment in certain circumstances).  The Preferred Shares have no expiration date.</footnote>
        <footnote id="F3">This Form 3 is also being filed by: (i) Oaktree Fund GP, LLC, a Delaware limited liability company (&quot;GP LLC&quot;), in its capacity as general partner of Organics; (ii) Oaktree Fund GP I, L.P., a Delaware limited partnership (&quot;GP I&quot;), in its capacity as managing member of GP LLC; (iii) Oaktree Capital I, L.P., a Delaware limited partnership (&quot;Capital I&quot;), in its capacity as general partner of GP I; (iv) OCM Holdings I, LLC, a Delaware limited liability company (&quot;Holdings I&quot;), in its capacity as general partner of Capital I; (v) Oaktree Holdings, LLC, a Delaware limited liability company (&quot;Holdings&quot;), in its capacity as managing member of Holdings I; (continued in footnote 4)</footnote>
        <footnote id="F4">(Continued from footnote 3) (vi) Oaktree Capital Group, LLC, a Delaware limited liability company (&quot;OCG&quot;), in its capacity as the managing member of Holdings; and (vii) Oaktree Capital Group Holdings GP, LLC, a Delaware limited liability company (&quot;OCGH GP&quot; and together with Organics, GP LLC, GP I, Capital I, Holdings I, Holdings and OCG, collectively, the &quot;Reporting Persons&quot;), in its capacity as the duly elected manager of OCG.</footnote>
        <footnote id="F5">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 3 shall not be construed as an admission that any such Reporting Person is the beneficial owner of any equity securities covered by this Form</footnote>
        <footnote id="F6">OCGH GP is managed by an executive committee consisting of Howard S. Marks, Bruce A. Karsh, Sheldon M. Stone, Stephen A. Kaplan, John B. Frank, David M. Kirchheimer, and Jay S. Wintrob (the &quot;OCGH GP Members&quot;). In such capacity, the OCGH GP Members may be deemed to have indirect beneficial ownership of the Preferred Shares and Special Voting Shares reported herein. Each OCGH GP Member expressly disclaims beneficial ownership of the Preferred Shares and Special Voting Shares reported herein, except to the extent of his respective pecuniary interests therein, and the filing of this Form 3 shall not be construed as an admission that any such person is the beneficial owner of any equity securities covered by this Form 3.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>See signatures included in Exhibit 99.1</signatureName>
        <signatureDate>2016-10-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
