diff --git a/index.js b/index.js
index f13c8c8..dbe57f2 100644
--- a/index.js
+++ b/index.js
@@ -63,19 +63,28 @@ async function action() {
         octokit,
         shouldAddComment,
         `Unknown exit_code input [${exitType}]. Must be one of: ${allowedExitCodes.join(
-          ", ",
-        )}`,
+          ", "
+        )}`
       );
       return;
     }
 
+    let issue_number = github.context.issue.number;
+
+    if (!issue_number && github.context.eventName == "merge_queue") {
+      // Parse out of the ref for merge queue
+      // e.g. refs/heads/gh-readonly-queue/main/pr-17-a3c310584587d4b97c2df0cb46fe050cc46a15d6
+      const lastPart = github.context.ref.split("/").pop();
+      issue_number = lastPart.match(/pr-(\d+)-/)[1];
+    }
+
     // Fetch the labels using the API
     // We use the API rather than read event.json in case earlier steps
     // added a label
     const labels = (
       await octokit.rest.issues.listLabelsOnIssue({
         ...github.context.repo,
-        issue_number: github.context.issue.number,
+        issue_number,
       })
     ).data;
 
diff --git a/index.test.js b/index.test.js
index 3ae51a1..afb9f5d 100644
--- a/index.test.js
+++ b/index.test.js
@@ -644,6 +644,60 @@ describe("Required Labels", () => {
 
       await action();
     });
+
+  });
+
+  describe("merge_queue", () => {
+    it("extracts the PR number from the ref if needed", async () => {
+      restoreTest = mockEvent(
+        "merge_queue",
+        {},
+        {
+          INPUT_LABELS: "enhancement",
+          INPUT_MODE: "exactly",
+          INPUT_COUNT: "1",
+          GITHUB_TOKEN: "mock-token-here-abc",
+        },
+        {
+          ref: "refs/heads/gh-readonly-queue/main/pr-28-a3c310584587d4b97c2df0cb46fe050cc46a15d6"
+        },
+      );
+
+      mockLabels(["enhancement", "bug"]);
+
+      await action();
+      expect(core.setOutput).toBeCalledTimes(2);
+      expect(core.setOutput).toBeCalledWith("status", "success");
+      expect(core.setOutput).toBeCalledWith("labels", "enhancement");
+    });
+
+    it("prefers the issue number that is set in the payload to extracting from a ref", async () => {
+      restoreTest = mockEvent(
+        "merge_queue",
+        {
+          issue: {
+            number: 28,
+          },
+        },
+        {
+          INPUT_LABELS: "enhancement",
+          INPUT_MODE: "exactly",
+          INPUT_COUNT: "1",
+          GITHUB_TOKEN: "mock-token-here-abc",
+        },
+        {
+          // This would lead to an error as there are no mocks for PR 999
+          ref: "refs/heads/gh-readonly-queue/main/pr-999-a3c310584587d4b97c2df0cb46fe050cc46a15d6"
+        },
+      );
+
+      mockLabels(["enhancement", "bug"]);
+
+      await action();
+      expect(core.setOutput).toBeCalledTimes(2);
+      expect(core.setOutput).toBeCalledWith("status", "success");
+      expect(core.setOutput).toBeCalledWith("labels", "enhancement");
+    });
   });
 });
 
@@ -683,8 +737,13 @@ function mockListComments(comments) {
     );
 }
 
-function mockEvent(eventName, mockPayload, additionalParams = {}) {
+function mockEvent(eventName, mockPayload, additionalParams, additionalContext = {}) {
   github.context.payload = mockPayload;
+  github.context.eventName = eventName;
+
+  for (const key in additionalContext) {
+    github.context[key] = additionalContext[key];
+  }
 
   const params = {
     GITHUB_EVENT_NAME: eventName,