diff --git a/actions/setup/js/add_reaction.cjs b/actions/setup/js/add_reaction.cjs
index 1c50697e86a..ad857c6324e 100644
--- a/actions/setup/js/add_reaction.cjs
+++ b/actions/setup/js/add_reaction.cjs
@@ -63,10 +63,11 @@ async function main() {
 
 /**
  * Resolve the REST API endpoint for non-discussion events.
- * Returns null for discussion/discussion_comment/unsupported events (handled separately).
+ * Returns null for discussion/discussion_comment/pull_request_review/unsupported events (handled separately).
  * @param {string} eventName
  * @param {string} owner
  * @param {string} repo
+ * @param {Record<string, any>} payload
  * @returns {string | null}
  */
 function resolveRestEndpoint(eventName, owner, repo, payload) {
@@ -108,6 +109,10 @@ function resolveRestEndpoint(eventName, owner, repo, payload) {
       return `/repos/${owner}/${repo}/pulls/comments/${reviewCommentId}/reactions`;
     }
 
+    case "pull_request_review":
+      // Reactions are not supported on review objects; skip silently.
+      return null;
+
     default:
       return null;
   }
@@ -126,6 +131,7 @@ function isRestReactionEvent(eventName) {
  * @param {string} eventName
  * @param {string} owner
  * @param {string} repo
+ * @param {Record<string, any>} payload
  * @param {string} reaction
  */
 async function handleGraphQLOrUnknownEvent(eventName, owner, repo, payload, reaction) {
diff --git a/actions/setup/js/add_reaction.test.cjs b/actions/setup/js/add_reaction.test.cjs
index 364a15936da..63402966f95 100644
--- a/actions/setup/js/add_reaction.test.cjs
+++ b/actions/setup/js/add_reaction.test.cjs
@@ -743,6 +743,13 @@ describe("add_reaction", () => {
       expect(mockCore.setFailed).not.toHaveBeenCalled();
     });
 
+    it("should return null without failure for pull_request_review even with empty payload", async () => {
+      const { resolveRestEndpoint } = await importHelpers();
+      expect(resolveRestEndpoint("pull_request_review", "o", "r", {})).toBeNull();
+      expect(mockCore.setFailed).not.toHaveBeenCalled();
+      expect(mockCore.error).not.toHaveBeenCalled();
+    });
+
     it("should return null for discussion events (handled via GraphQL)", async () => {
       global.context = { eventName: "discussion", repo: { owner: "o", repo: "r" }, payload: { discussion: { number: 3 } } };
       const { resolveRestEndpoint } = await importHelpers();