diff --git a/app/assets/stylesheets/framework/animations.scss b/app/assets/stylesheets/framework/animations.scss
index 8d38fc78a191321666c32f133670c0e4b6fddd58..f1ff9faef7f30c6788a63326d9fc806238a913bf 100644
--- a/app/assets/stylesheets/framework/animations.scss
+++ b/app/assets/stylesheets/framework/animations.scss
@@ -71,6 +71,27 @@
   transition: $unfoldedTransitions;
 }
 
+@mixin disableAllAnimation {
+  /*CSS transitions*/
+  -o-transition-property: none !important;
+  -moz-transition-property: none !important;
+  -ms-transition-property: none !important;
+  -webkit-transition-property: none !important;
+  transition-property: none !important;
+  /*CSS transforms*/
+  -o-transform: none !important;
+  -moz-transform: none !important;
+  -ms-transform: none !important;
+  -webkit-transform: none !important;
+  transform: none !important;
+  /*CSS animations*/
+  -webkit-animation: none !important;
+  -moz-animation: none !important;
+  -o-animation: none !important;
+  -ms-animation: none !important;
+  animation: none !important;
+}
+
 @function unfoldTransition ($transition) {
   // Default values
   $property: all;
diff --git a/app/assets/stylesheets/framework/markdown_area.scss b/app/assets/stylesheets/framework/markdown_area.scss
index 5bff694658cd2a3666658707e65df5f2eb854968..d4758d9035208b6e4d5e51aae57f671fab4be8b5 100644
--- a/app/assets/stylesheets/framework/markdown_area.scss
+++ b/app/assets/stylesheets/framework/markdown_area.scss
@@ -159,6 +159,7 @@
   .cur {
     .avatar {
       border: 1px solid $white-light;
+      @include disableAllAnimation;
     }
   }
 }
diff --git a/changelogs/unreleased/27602-fix-avatar-border-flicker-mention-dropdown.yml b/changelogs/unreleased/27602-fix-avatar-border-flicker-mention-dropdown.yml
new file mode 100644
index 0000000000000000000000000000000000000000..a5bb37ec8a942bb9ecbecda5cf13475990921a29
--- /dev/null
+++ b/changelogs/unreleased/27602-fix-avatar-border-flicker-mention-dropdown.yml
@@ -0,0 +1,4 @@
+---
+title: Fixes flickering of avatar border in mention dropdown
+merge_request: 8950
+author: