diff --git a/web_src/js/index.js b/web_src/js/index.js
index b8d6578c34..61059b6946 100644
--- a/web_src/js/index.js
+++ b/web_src/js/index.js
@@ -1226,25 +1226,41 @@ function initPullRequestReview() {
       $(this).closest('tr').removeClass('focus-lines-new focus-lines-old');
     });
   $('.add-code-comment').on('click', function (e) {
-    // https://github.com/go-gitea/gitea/issues/4745
-    if ($(e.target).hasClass('btn-add-single')) {
-      return;
-    }
+    if ($(e.target).hasClass('btn-add-single')) return; // https://github.com/go-gitea/gitea/issues/4745
     e.preventDefault();
+
     const isSplit = $(this).closest('.code-diff').hasClass('code-diff-split');
     const side = $(this).data('side');
     const idx = $(this).data('idx');
     const path = $(this).data('path');
     const form = $('#pull_review_add_comment').html();
     const tr = $(this).closest('tr');
+
+    const oldLineNum = tr.find('.lines-num-old').data('line-num');
+    const newLineNum = tr.find('.lines-num-new').data('line-num');
+    const addCommentKey = `${oldLineNum}|${newLineNum}`;
+    if (document.querySelector(`[data-add-comment-key="${addCommentKey}"]`)) return; // don't add same comment box twice
+
     let ntr = tr.next();
     if (!ntr.hasClass('add-comment')) {
-      ntr = $(`<tr class="add-comment">${
-        isSplit ? '<td class="lines-num"></td><td class="lines-type-marker"></td><td class="add-comment-left"></td><td class="lines-num"></td><td class="lines-type-marker"></td><td class="add-comment-right"></td>' :
-          '<td class="lines-num"></td><td class="lines-num"></td><td class="add-comment-left add-comment-right" colspan="2"></td>'
-      }</tr>`);
+      ntr = $(`
+        <tr class="add-comment" data-add-comment-key="${addCommentKey}">
+          ${isSplit ? `
+            <td class="lines-num"></td>
+            <td class="lines-type-marker"></td>
+            <td class="add-comment-left"></td>
+            <td class="lines-num"></td>
+            <td class="lines-type-marker"></td>
+            <td class="add-comment-right"></td>
+          ` : `
+            <td class="lines-num"></td>
+            <td class="lines-num"></td>
+            <td class="add-comment-left add-comment-right" colspan="2"></td>
+          `}
+        </tr>`);
       tr.after(ntr);
     }
+
     const td = ntr.find(`.add-comment-${side}`);
     let commentCloud = td.find('.comment-code-cloud');
     if (commentCloud.length === 0) {