diff --git a/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api.ts b/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api.ts
index 166f27e..5210616 100644
--- a/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api.ts
+++ b/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api.ts
@@ -30,6 +30,7 @@
   NumericChangeId,
   PathToCommentsInfoMap,
   FileInfo,
+  ParentPatchSetNum,
 } from '../../../types/common';
 import {hasOwnProperty} from '../../../utils/common-util';
 import {
@@ -367,6 +368,10 @@
    * does not return the range of the ported thread and it becomes a file level
    * thread.
    *
+   * If a comment was created with Side=PARENT, then we only show this ported
+   * comment if Base is part of the patch range, always on the left side of
+   * the diff.
+   *
    * @return only the ported threads for the specified file and patch range
    */
   _getPortedCommentThreads(
@@ -405,15 +410,22 @@
         return false;
       }
 
-      // TODO(dhruvsri): Add handling for thread.commentSide = PARENT
-      if (thread.commentSide === CommentSide.PARENT) return false;
+      thread.diffSide = Side.RIGHT;
+      if (thread.commentSide === CommentSide.PARENT) {
+        // TODO(dhruvsri): Add handling for merge parents
+        if (
+          patchRange.basePatchNum !== ParentPatchSetNum ||
+          !!thread.mergeParentNum
+        )
+          return false;
+        thread.diffSide = Side.LEFT;
+      }
 
       if (!isUnresolved(thread) && !isDraftThread(thread)) return false;
 
       thread.range = portedComment.range;
       thread.line = portedComment.line;
       thread.ported = true;
-      thread.diffSide = Side.RIGHT;
       return true;
     });
   }
diff --git a/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api_test.js b/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api_test.js
index dd36613..e107c16 100644
--- a/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api_test.js
+++ b/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api_test.js
@@ -20,6 +20,7 @@
 import {ChangeComments} from './gr-comment-api.js';
 import {isInRevisionOfPatchRange, isInBaseOfPatchRange, isDraftThread, isUnresolved, createCommentThreads} from '../../../utils/comment-util.js';
 import {createDraft, createComment, createChangeComments, createCommentThread} from '../../../test/test-data-generators.js';
+import {CommentSide, Side} from '../../../constants/constants.js';
 
 const basicFixture = fixtureFromElement('gr-comment-api');
 
@@ -153,7 +154,7 @@
       const comment1 = {
         ...createComment(),
         unresolved: true,
-        id: 'db977012_e1f13818',
+        id: '1',
         line: 136,
         patch_set: 2,
         range: {
@@ -167,10 +168,22 @@
       const comment2 = {
         ...createComment(),
         patch_set: 2,
-        id: 'ecf0b9fa_fe1a5f62',
+        id: '2',
         line: 5,
       };
 
+      const comment3 = {
+        ...createComment(),
+        side: CommentSide.PARENT,
+        line: 10,
+        unresolved: true,
+      };
+
+      const comment4 = {
+        ...comment3,
+        parent: -2,
+      };
+
       const draft1 = {
         ...createDraft(),
         id: 'db977012_e1f13828',
@@ -277,6 +290,74 @@
         ).length, 0);
       });
 
+      test('comments with side=PARENT are ported over', () => {
+        changeComments = new ChangeComments(
+            {/* comments */
+              // comment left on Base
+              'karma.conf.js': [comment3],
+            },
+            {}/* robot comments */,
+            {/* drafts */
+              'karma.conf.js': [draft2],
+            },
+            {/* ported comments */
+              'karma.conf.js': [{
+                ...comment3,
+                line: 31,
+                patch_set: 4,
+              }],
+            },
+            {}/* ported drafts */
+        );
+
+        const portedThreads = changeComments._getPortedCommentThreads(
+            {path: 'karma.conf.js'}, {patchNum: 4, basePatchNum: 'PARENT'});
+        assert.equal(portedThreads.length, 1);
+        assert.equal(portedThreads[0].line, 31);
+        assert.equal(portedThreads[0].diffSide, Side.LEFT);
+
+        assert.equal(changeComments._getPortedCommentThreads(
+            {path: 'karma.conf.js'}, {patchNum: 4, basePatchNum: -2}
+        ).length, 0);
+
+        assert.equal(changeComments._getPortedCommentThreads(
+            {path: 'karma.conf.js'}, {patchNum: 4, basePatchNum: 2}
+        ).length, 0);
+      });
+
+      test('comments left on merge parent is not ported over', () => {
+        changeComments = new ChangeComments(
+            {/* comments */
+              // comment left on Base
+              'karma.conf.js': [comment4],
+            },
+            {}/* robot comments */,
+            {/* drafts */
+              'karma.conf.js': [draft2],
+            },
+            {/* ported comments */
+              'karma.conf.js': [{
+                ...comment4,
+                line: 31,
+                patch_set: 4,
+              }],
+            },
+            {}/* ported drafts */
+        );
+
+        const portedThreads = changeComments._getPortedCommentThreads(
+            {path: 'karma.conf.js'}, {patchNum: 4, basePatchNum: 'PARENT'});
+        assert.equal(portedThreads.length, 0);
+
+        assert.equal(changeComments._getPortedCommentThreads(
+            {path: 'karma.conf.js'}, {patchNum: 4, basePatchNum: -2}
+        ).length, 0);
+
+        assert.equal(changeComments._getPortedCommentThreads(
+            {path: 'karma.conf.js'}, {patchNum: 4, basePatchNum: 2}
+        ).length, 0);
+      });
+
       test('ported comments contribute to comment count', () => {
         assert.equal(changeComments.computeCommentsString(
             {basePatchNum: 'PARENT', patchNum: 2}, 'karma.conf.js',