diff --git a/src/libs/ReportUtils.js b/src/libs/ReportUtils.js
index 54c69c630714..82d3f3217dff 100644
--- a/src/libs/ReportUtils.js
+++ b/src/libs/ReportUtils.js
@@ -1339,6 +1339,49 @@ function buildOptimisticAddCommentReportAction(text, file) {
     };
 }
 
+/**
+ * update optimistic parent reportAction when a comment is added or remove in the child report
+ * @param {String} parentReportAction - Parent report action of the child report
+ * @param {String} lastVisibleActionCreated - Last visible action created of the child report
+ * @param {String} type - The type of action in the child report
+ * @returns {Object}
+ */
+
+function updateOptimisticParentReportAction(parentReportAction, lastVisibleActionCreated, type) {
+    let childVisibleActionCount = parentReportAction.childVisibleActionCount || 0;
+    let childCommenterCount = parentReportAction.childCommenterCount || 0;
+    let childOldestFourAccountIDs = parentReportAction.childOldestFourAccountIDs;
+
+    if (type === CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD) {
+        childVisibleActionCount += 1;
+        const oldestFourAccountIDs = childOldestFourAccountIDs ? childOldestFourAccountIDs.split(',') : [];
+        if (oldestFourAccountIDs.length < 4) {
+            const index = _.findIndex(oldestFourAccountIDs, (accountID) => accountID === currentUserAccountID.toString());
+            if (index === -1) {
+                childCommenterCount += 1;
+                oldestFourAccountIDs.push(currentUserAccountID);
+            }
+        }
+        childOldestFourAccountIDs = oldestFourAccountIDs.join(',');
+    } else if (type === CONST.RED_BRICK_ROAD_PENDING_ACTION.DELETE) {
+        if (childVisibleActionCount > 0) {
+            childVisibleActionCount -= 1;
+        }
+
+        if (childVisibleActionCount === 0) {
+            childCommenterCount = 0;
+            childOldestFourAccountIDs = '';
+        }
+    }
+
+    return {
+        childVisibleActionCount,
+        childCommenterCount,
+        childLastVisibleActionCreated: lastVisibleActionCreated,
+        childOldestFourAccountIDs,
+    };
+}
+
 /**
  * Builds an optimistic reportAction for the parent report when a task is created
  * @param {String} taskReportID - Report ID of the task
@@ -2549,6 +2592,7 @@ export {
     buildOptimisticTaskReportAction,
     buildOptimisticAddCommentReportAction,
     buildOptimisticTaskCommentReportAction,
+    updateOptimisticParentReportAction,
     shouldReportBeInOptionList,
     getChatByParticipants,
     getChatByParticipantsByLoginList,
diff --git a/src/libs/actions/Report.js b/src/libs/actions/Report.js
index 8c072d8c7bc8..4d4c9290d87c 100644
--- a/src/libs/actions/Report.js
+++ b/src/libs/actions/Report.js
@@ -320,6 +320,21 @@ function addActions(reportID, text = '', file) {
         },
     ];
 
+    // Optimistically update the parent report action if the report is a thread
+    const report = ReportUtils.getReport(reportID);
+    if (report && report.parentReportActionID) {
+        const parentReportAction = ReportActionsUtils.getParentReportAction(report);
+        if (parentReportAction && parentReportAction.reportActionID) {
+            optimisticData.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${report.parentReportID}`,
+                value: {
+                    [parentReportAction.reportActionID]: ReportUtils.updateOptimisticParentReportAction(parentReportAction, currentTime, CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD),
+                },
+            });
+        }
+    }
+
     // Update the timezone if it's been 5 minutes from the last time the user added a comment
     if (DateUtils.canUpdateTimezone()) {
         const timezone = DateUtils.getCurrentTimezone();
@@ -926,6 +941,24 @@ function deleteReportComment(reportID, reportAction) {
         },
     ];
 
+    const report = ReportUtils.getReport(reportID);
+    if (report && report.parentReportActionID) {
+        const parentReportAction = ReportActionsUtils.getParentReportAction(report);
+        if (parentReportAction && parentReportAction.reportActionID) {
+            optimisticData.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${report.parentReportID}`,
+                value: {
+                    [parentReportAction.reportActionID]: ReportUtils.updateOptimisticParentReportAction(
+                        parentReportAction,
+                        optimisticReport.lastVisibleActionCreated,
+                        CONST.RED_BRICK_ROAD_PENDING_ACTION.DELETE,
+                    ),
+                },
+            });
+        }
+    }
+
     const parameters = {
         reportID: originalReportID,
         reportActionID,