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

    <schemaVersion>X0607</schemaVersion>

    <documentType>3/A</documentType>

    <periodOfReport>2026-06-30</periodOfReport>

    <dateOfOriginalSubmission>2026-06-30</dateOfOriginalSubmission>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001699963</issuerCik>
        <issuerName>Neutron Holdings, Inc.</issuerName>
        <issuerTradingSymbol>LIME</issuerTradingSymbol>
        <issuerForeignTradingSymbol></issuerForeignTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001542371</rptOwnerCik>
            <rptOwnerName>Ryan Michael S.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>false</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>C/O NEUTRON HOLDINGS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>444 TOWNSEND STREET, FL 1</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94107</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Accounting Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>26785</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">This Form is filed solely as an amendment to the Form 3 filed on June 30, 2026. This amendment amends and restates the first footnote in Table I  to resolve a clerical error as follows: &quot;Represents restricted stock units (&quot;RSUs&quot;), each of which represents a contingent right to receive one share of Common Stock of the Issuer. The RSUs vest in approximately equal quarterly installments over three years, subject to the Reporting Person's continuous service with the Issuer.&quot; Except as set forth in this amendment, the original Form 3 filed is unchanged and no amendment is made hereby to any other footnotes of the initial Form 3.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Susie Giordano, Attorney-in-Fact</signatureName>
        <signatureDate>2026-09-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
