diff --git a/app/assets/javascripts/notes.js b/app/assets/javascripts/notes.js
index 55391ebc089..80adf8f0885 100644
--- a/app/assets/javascripts/notes.js
+++ b/app/assets/javascripts/notes.js
@@ -175,7 +175,7 @@ const normalizeNewlines = function(str) {
           if ($textarea.val() !== '') {
             return;
           }
-          myLastNote = $("li.note[data-author-id='" + gon.current_user_id + "'][data-editable]:last");
+          myLastNote = $(`li.note[data-author-id='${gon.current_user_id}'][data-editable]:last`, $textarea.closest('.note, #notes'));
           if (myLastNote.length) {
             myLastNoteEditBtn = myLastNote.find('.js-note-edit');
             return myLastNoteEditBtn.trigger('click', [true, myLastNote]);
diff --git a/changelogs/unreleased/up-arrow-focus-discussion-comment.yml b/changelogs/unreleased/up-arrow-focus-discussion-comment.yml
new file mode 100644
index 00000000000..5457dab6d3d
--- /dev/null
+++ b/changelogs/unreleased/up-arrow-focus-discussion-comment.yml
@@ -0,0 +1,4 @@
+---
+title: Fix up arrow not editing last discussion comment
+merge_request:
+author:
diff --git a/spec/javascripts/fixtures/merge_requests.rb b/spec/javascripts/fixtures/merge_requests.rb
index 47d904b865b..a746a776548 100644
--- a/spec/javascripts/fixtures/merge_requests.rb
+++ b/spec/javascripts/fixtures/merge_requests.rb
@@ -16,6 +16,16 @@ describe Projects::MergeRequestsController, '(JavaScript fixtures)', type: :cont
       sha: merge_request.diff_head_sha
     )
   end
+  let(:path) { "files/ruby/popen.rb" }
+  let(:position) do
+    Gitlab::Diff::Position.new(
+      old_path: path,
+      new_path: path,
+      old_line: nil,
+      new_line: 14,
+      diff_refs: merge_request.diff_refs
+    )
+  end
 
   render_views
 
@@ -39,6 +49,12 @@ describe Projects::MergeRequestsController, '(JavaScript fixtures)', type: :cont
     render_merge_request(example.description, merged_merge_request)
   end
 
+  it 'merge_requests/diff_comment.html.raw' do |example|
+    create(:diff_note_on_merge_request, project: project, author: admin, position: position, noteable: merge_request)
+    create(:note_on_merge_request, author: admin, project: project, noteable: merge_request)
+    render_merge_request(example.description, merge_request)
+  end
+
   private
 
   def render_merge_request(fixture_file_name, merge_request)
diff --git a/spec/javascripts/merge_request_notes_spec.js b/spec/javascripts/merge_request_notes_spec.js
new file mode 100644
index 00000000000..86a4a70da42
--- /dev/null
+++ b/spec/javascripts/merge_request_notes_spec.js
@@ -0,0 +1,61 @@
+/* global Notes */
+
+import 'vendor/autosize';
+import '~/gl_form';
+import '~/lib/utils/text_utility';
+import '~/render_gfm';
+import '~/render_math';
+import '~/notes';
+
+fdescribe('Merge request notes', () => {
+  window.gon = window.gon || {};
+  window.gl = window.gl || {};
+  gl.utils = gl.utils || {};
+
+  const fixture = 'merge_requests/diff_comment.html.raw';
+  preloadFixtures(fixture);
+
+  beforeEach(() => {
+    loadFixtures(fixture);
+    gl.utils.disableButtonIfEmptyField = _.noop;
+    window.project_uploads_path = 'http://test.host/uploads';
+    $('body').data('page', 'projects:merge_requests:show');
+    window.gon.current_user_id = $('.note:last').data('author-id');
+
+    return new Notes('', []);
+  });
+
+  describe('up arrow', () => {
+    it('edits last comment when triggered in main form', () => {
+      const upArrowEvent = $.Event('keydown');
+      upArrowEvent.which = 38;
+
+      spyOnEvent('.note:last .js-note-edit', 'click');
+
+      $('.js-note-text').trigger(upArrowEvent);
+
+      expect('click').toHaveBeenTriggeredOn('.note:last .js-note-edit');
+    });
+
+    it('edits last comment in discussion when triggered in discussion form', (done) => {
+      const upArrowEvent = $.Event('keydown');
+      upArrowEvent.which = 38;
+
+      spyOnEvent('.note-discussion .js-note-edit', 'click');
+
+      $('.js-discussion-reply-button').click();
+
+      setTimeout(() => {
+        expect(
+          $('.note-discussion .js-note-text'),
+        ).toExist();
+
+        $('.note-discussion .js-note-text').trigger(upArrowEvent);
+
+        expect('click').toHaveBeenTriggeredOn('.note-discussion .js-note-edit');
+
+        done();
+      });
+    });
+  });
+});