diff --git a/src/libs/actions/Report/index.ts b/src/libs/actions/Report/index.ts
index 0d160972372e..a7adf620070a 100644
--- a/src/libs/actions/Report/index.ts
+++ b/src/libs/actions/Report/index.ts
@@ -159,7 +159,9 @@ import {
     isExpenseReport,
     isGroupChat as isGroupChatReportUtils,
     isHiddenForCurrentUser,
+    isInvoiceReport,
     isIOUReportUsingReport,
+    isMoneyRequestReport,
     isOpenExpenseReport,
     isProcessingReport,
     isReportManuallyReimbursed,
@@ -5496,7 +5498,20 @@ function resolveActionableMentionWhisper(
 
     // When the action belongs to a child report (e.g. a one-transaction thread), also update
     // the parent report's participants so the members list the user is viewing updates immediately.
-    const parentInviteData = isInviteResolution && parentReport?.reportID && parentReport.reportID !== reportID ? buildParticipantsInviteData(parentReport, inviteeAccountIDs) : undefined;
+    // When parentReport is the same as the current report (e.g. viewing a transaction thread directly),
+    // fall back to the report's parentReportID to find the actual ancestor (IOU/expense/invoice report).
+    const isParentReportDifferent = !!parentReport?.reportID && parentReport.reportID !== reportID;
+    let parentInviteData = isInviteResolution && isParentReportDifferent ? buildParticipantsInviteData(parentReport, inviteeAccountIDs) : undefined;
+    if (!parentInviteData && isInviteResolution && report?.parentReportID && report.parentReportID !== reportID) {
+        const ancestorReport = allReports?.[`${ONYXKEYS.COLLECTION.REPORT}${report.parentReportID}`];
+        if (ancestorReport && (isMoneyRequestReport(ancestorReport) || isInvoiceReport(ancestorReport))) {
+            parentInviteData = buildParticipantsInviteData(ancestorReport, inviteeAccountIDs);
+        }
+    }
+    let parentReportIDForUpdate: string | undefined;
+    if (parentInviteData) {
+        parentReportIDForUpdate = isParentReportDifferent ? parentReport.reportID : report?.parentReportID;
+    }
     const parentParticipantsOptimisticData = parentInviteData?.optimistic;
     const parentParticipantsFailureData = parentInviteData?.failure;
 
@@ -5523,10 +5538,10 @@ function resolveActionableMentionWhisper(
         },
     ];
 
-    if (parentParticipantsOptimisticData && parentReport?.reportID) {
+    if (parentParticipantsOptimisticData && parentReportIDForUpdate) {
         optimisticData.push({
             onyxMethod: Onyx.METHOD.MERGE,
-            key: `${ONYXKEYS.COLLECTION.REPORT}${parentReport.reportID}`,
+            key: `${ONYXKEYS.COLLECTION.REPORT}${parentReportIDForUpdate}`,
             value: parentParticipantsOptimisticData,
         });
     }
@@ -5554,10 +5569,10 @@ function resolveActionableMentionWhisper(
         },
     ];
 
-    if (parentParticipantsFailureData && parentReport?.reportID) {
+    if (parentParticipantsFailureData && parentReportIDForUpdate) {
         failureData.push({
             onyxMethod: Onyx.METHOD.MERGE,
-            key: `${ONYXKEYS.COLLECTION.REPORT}${parentReport.reportID}`,
+            key: `${ONYXKEYS.COLLECTION.REPORT}${parentReportIDForUpdate}`,
             value: parentParticipantsFailureData,
         });
     }
diff --git a/tests/actions/ReportTest.ts b/tests/actions/ReportTest.ts
index c6cf26b29e6f..ead0698ffbd6 100644
--- a/tests/actions/ReportTest.ts
+++ b/tests/actions/ReportTest.ts
@@ -7440,6 +7440,85 @@ describe('actions/Report', () => {
             });
         });
 
+        it('should fall back to ancestor report via parentReportID when parentReport matches current report', async () => {
+            global.fetch = TestHelper.getGlobalFetchMock();
+
+            const TRANSACTION_THREAD_ID = '20';
+            const ANCESTOR_IOU_REPORT_ID = '21';
+            const WHISPER_ACTION_ID = '20001';
+            const EXISTING_PARTICIPANT_ID = 100;
+            const INVITEE_ACCOUNT_ID = 200;
+
+            // Transaction thread report — parentReportID points to the IOU ancestor
+            const transactionThreadReport: OnyxTypes.Report = {
+                ...createRandomReport(20, undefined),
+                reportID: TRANSACTION_THREAD_ID,
+                parentReportID: ANCESTOR_IOU_REPORT_ID,
+                participants: {
+                    [EXISTING_PARTICIPANT_ID]: {
+                        notificationPreference: CONST.REPORT.NOTIFICATION_PREFERENCE.ALWAYS,
+                        role: CONST.REPORT.ROLE.ADMIN,
+                    },
+                },
+                lastMessageText: 'Receipt',
+                lastVisibleActionCreated: '2024-11-19 08:04:13.728',
+                lastActorAccountID: EXISTING_PARTICIPANT_ID,
+            };
+
+            // Ancestor IOU report (money request report)
+            const ancestorIOUReport: OnyxTypes.Report = {
+                ...createRandomReport(21, undefined),
+                reportID: ANCESTOR_IOU_REPORT_ID,
+                type: CONST.REPORT.TYPE.IOU,
+                participants: {
+                    [EXISTING_PARTICIPANT_ID]: {
+                        notificationPreference: CONST.REPORT.NOTIFICATION_PREFERENCE.ALWAYS,
+                        role: CONST.REPORT.ROLE.ADMIN,
+                    },
+                },
+            };
+
+            const whisperAction = {
+                reportActionID: WHISPER_ACTION_ID,
+                reportID: TRANSACTION_THREAD_ID,
+                actionName: CONST.REPORT.ACTIONS.TYPE.ACTIONABLE_MENTION_WHISPER,
+                created: '2024-11-19 08:04:13.730',
+                message: [{html: 'Mentioned @user1', text: 'Mentioned @user1', type: 'COMMENT'}],
+                originalMessage: {
+                    inviteeAccountIDs: [INVITEE_ACCOUNT_ID],
+                    inviteeEmails: ['user1@example.com'],
+                    whisperedTo: [EXISTING_PARTICIPANT_ID],
+                },
+            } as unknown as OnyxTypes.ReportAction;
+
+            await Onyx.merge(`${ONYXKEYS.COLLECTION.REPORT}${TRANSACTION_THREAD_ID}`, transactionThreadReport);
+            await Onyx.merge(`${ONYXKEYS.COLLECTION.REPORT}${ANCESTOR_IOU_REPORT_ID}`, ancestorIOUReport);
+            await Onyx.mergeCollection(ONYXKEYS.COLLECTION.REPORT_ACTIONS, {
+                [`${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${TRANSACTION_THREAD_ID}`]: {
+                    [WHISPER_ACTION_ID]: whisperAction,
+                },
+            });
+            await waitForBatchedUpdates();
+
+            // Pass parentReport as the same report (simulating viewing transaction thread directly)
+            Report.resolveActionableMentionWhisper(transactionThreadReport, whisperAction, CONST.REPORT.ACTIONABLE_MENTION_WHISPER_RESOLUTION.INVITE, false, transactionThreadReport);
+            await waitForBatchedUpdates();
+
+            // Verify the invitee was added to the transaction thread participants
+            const updatedThreadReport = await getOnyxValue(`${ONYXKEYS.COLLECTION.REPORT}${TRANSACTION_THREAD_ID}` as const);
+            expect(updatedThreadReport?.participants?.[INVITEE_ACCOUNT_ID]).toMatchObject({
+                notificationPreference: CONST.REPORT.NOTIFICATION_PREFERENCE.ALWAYS,
+                role: CONST.REPORT.ROLE.MEMBER,
+            });
+
+            // Verify the invitee was also added to the ancestor IOU report via the fallback path
+            const updatedAncestorReport = await getOnyxValue(`${ONYXKEYS.COLLECTION.REPORT}${ANCESTOR_IOU_REPORT_ID}` as const);
+            expect(updatedAncestorReport?.participants?.[INVITEE_ACCOUNT_ID]).toMatchObject({
+                notificationPreference: CONST.REPORT.NOTIFICATION_PREFERENCE.ALWAYS,
+                role: CONST.REPORT.ROLE.MEMBER,
+            });
+        });
+
         it('should remove optimistically added participants on failure rollback', async () => {
             const mockFetch = TestHelper.getGlobalFetchMock() as MockFetch;
             global.fetch = mockFetch;