diff --git a/web/chat/inline-engagement.css b/web/chat/inline-engagement.css
--- a/web/chat/inline-engagement.css
+++ b/web/chat/inline-engagement.css
@@ -42,6 +42,11 @@
   background: var(--inline-engagement-bg-hover);
 }
 
+a.reactionContainerSelected {
+  border: 1px solid var(--inline-engagement-color);
+  padding: 3px 7px;
+}
+
 div.unread {
   font-weight: bold;
 }
diff --git a/web/chat/inline-engagement.react.js b/web/chat/inline-engagement.react.js
--- a/web/chat/inline-engagement.react.js
+++ b/web/chat/inline-engagement.react.js
@@ -100,12 +100,18 @@
     }
 
     return Object.keys(reactions).map(reaction => {
-      const numOfReacts = reactions[reaction].users.length;
+      const reactionInfo = reactions[reaction];
+      const numOfReacts = reactionInfo.users.length;
+
+      const reactionClassName = classNames({
+        [css.reactionContainer]: true,
+        [css.reactionContainerSelected]: reactionInfo.viewerReacted,
+      });
 
       return (
         <a
           onClick={event => onClickReaction(event, reaction)}
-          className={css.reactionContainer}
+          className={reactionClassName}
           key={reaction}
         >
           {`${reaction} ${numOfReacts}`}