diff --git a/server/plugin/test_utils.go b/server/plugin/test_utils.go
index 3a4f76373..5f3e33e68 100644
--- a/server/plugin/test_utils.go
+++ b/server/plugin/test_utils.go
@@ -303,6 +303,12 @@ func GetMockPullRequestReviewCommentEvent(action, body, sender string) *github.P
 	}
 }
 
+func GetMockPullRequestReviewCommentReplyEvent(action, body, sender string, replyTo int64) *github.PullRequestReviewCommentEvent {
+	event := GetMockPullRequestReviewCommentEvent(action, body, sender)
+	event.Comment.InReplyTo = github.Int64(replyTo)
+	return event
+}
+
 func GetMockIssueCommentEvent(action, body, sender string) *github.IssueCommentEvent {
 	return &github.IssueCommentEvent{
 		Action: github.String(action),
diff --git a/server/plugin/webhook.go b/server/plugin/webhook.go
index c26da4d6e..c169d1ab6 100644
--- a/server/plugin/webhook.go
+++ b/server/plugin/webhook.go
@@ -1151,6 +1151,11 @@ func (p *Plugin) handleReviewCommentAuthorNotification(event *github.PullRequest
 		return
 	}
 
+	// Top-level comments on a submitted review are already DMed via handlePullRequestReviewNotification.
+	if event.GetComment().GetInReplyTo() == 0 {
+		return
+	}
+
 	authorUserID := p.getGitHubToUserIDMapping(author)
 	if authorUserID == "" {
 		return
diff --git a/server/plugin/webhook_test.go b/server/plugin/webhook_test.go
index 1f1b9b404..55f553a84 100644
--- a/server/plugin/webhook_test.go
+++ b/server/plugin/webhook_test.go
@@ -611,12 +611,17 @@ func TestHandleReviewCommentAuthorNotification(t *testing.T) {
 		},
 		{
 			name:  "Sender is the PR author",
-			event: GetMockPullRequestReviewCommentEvent(actionCreated, "body", MockIssueAuthor),
+			event: GetMockPullRequestReviewCommentReplyEvent(actionCreated, "body", MockIssueAuthor, 99),
 			setup: func(_ *plugintest.API, _ *mocks.MockKvStore) {},
 		},
 		{
-			name:  "Author not mapped to Mattermost",
+			name:  "Top-level review comment is covered by the review submitted notification",
 			event: GetMockPullRequestReviewCommentEvent(actionCreated, "body", MockUserLogin),
+			setup: func(_ *plugintest.API, _ *mocks.MockKvStore) {},
+		},
+		{
+			name:  "Author not mapped to Mattermost",
+			event: GetMockPullRequestReviewCommentReplyEvent(actionCreated, "body", MockUserLogin, 99),
 			setup: func(_ *plugintest.API, mockKVStore *mocks.MockKvStore) {
 				mockKVStore.EXPECT().Get("issueAuthor_githubusername", mock.MatchedBy(func(val any) bool {
 					_, ok := val.(*[]uint8)
@@ -625,8 +630,8 @@ func TestHandleReviewCommentAuthorNotification(t *testing.T) {
 			},
 		},
 		{
-			name:  "Successful author notification",
-			event: GetMockPullRequestReviewCommentEvent(actionCreated, "body", MockUserLogin),
+			name:  "Successful author notification for thread reply",
+			event: GetMockPullRequestReviewCommentReplyEvent(actionCreated, "body", MockUserLogin, 99),
 			setup: func(mockAPI *plugintest.API, mockKVStore *mocks.MockKvStore) {
 				mockKVStore.EXPECT().Get("issueAuthor_githubusername", mock.MatchedBy(func(val any) bool {
 					_, ok := val.(*[]uint8)
@@ -646,7 +651,7 @@ func TestHandleReviewCommentAuthorNotification(t *testing.T) {
 		},
 		{
 			name:  "Muted sender suppresses author notification",
-			event: GetMockPullRequestReviewCommentEvent(actionCreated, "body", MockUserLogin),
+			event: GetMockPullRequestReviewCommentReplyEvent(actionCreated, "body", MockUserLogin, 99),
 			setup: func(_ *plugintest.API, mockKVStore *mocks.MockKvStore) {
 				mockKVStore.EXPECT().Get("issueAuthor_githubusername", mock.MatchedBy(func(val any) bool {
 					_, ok := val.(*[]uint8)