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

    <schemaVersion>X0609</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2026-09-14</periodOfReport>

    <issuer>
        <issuerCik>0001979414</issuerCik>
        <issuerName>NEONC TECHNOLOGIES HOLDINGS, INC.</issuerName>
        <issuerTradingSymbol>NTHI</issuerTradingSymbol>
        <issuerForeignTradingSymbol></issuerForeignTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001997371</rptOwnerCik>
            <rptOwnerName>GARNETT KEITHLY</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>false</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>23975 SORRENTO PARK</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 205</rptOwnerStreet2>
            <rptOwnerCity>CALABASAS</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>91302</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>false</isDirector>
            <isOfficer>true</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle>CFO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2026-09-14</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>257</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.8948</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>242357</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>44053</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F4"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By HCWG LLC.</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The aggregate number of shares (the &quot;Shares&quot;) of common stock of Issuer purchased by the Reporting Person on the same date at different prices.</footnote>
        <footnote id="F2">Represents the weighted average purchase price. The Shares were purchased at prices ranging from $3.87 to $3.92 per share, inclusive. Full information regarding the number of Shares purchased at each price shall be provided to the Securities and Exchange Commission staff, Issuer or any security holder, upon request.</footnote>
        <footnote id="F3">Includes shares of common stock held by certain members of Reporting Person's immediate family of which Reporting Person disclaims beneficial ownership except to the extent of his pecuniary interest, if any, therein.</footnote>
        <footnote id="F4">Reporting Person is the beneficial onwer of such shares by virtue of being the sole member of The Hilkiah Group LLC (&quot;Hilkiah&quot;), which holds a 4.3% interest in HCWG LLC, a Delaware limited liability company (&quot;HCWG&quot;). HCWG is the direct holder of such shares.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/S/ KEITHLY GARNETT</signatureName>
        <signatureDate>2026-09-15</signatureDate>
    </ownerSignature>
</ownershipDocument>
