diff --git a/package/server.js b/package/server.js
index 8439af4..d709daa 100644
--- a/package/server.js
+++ b/package/server.js
@@ -204,7 +204,14 @@ function clientTests() {
 }
 
 // Before Meteor calls the `start` function, app tests will be parsed and loaded by Mocha
-function start() {
+async function start() {
+  // Wait for all Meteor.startup() callbacks (including async ones) to complete.
+  // In Meteor 3.x, async startup callbacks and top-level await can cause the
+  // startup queue to still be draining when the test driver's start() is called.
+  // Adding a callback at the end of the queue ensures it runs after all prior
+  // callbacks have finished. See: https://github.com/Meteor-Community-Packages/meteor-mocha/issues/176
+  await new Promise(resolve => Meteor.startup(resolve));
+
   const args = setArgs();
   runnerOptions = args.runnerOptions;
   coverageOptions = args.coverageOptions;
diff --git a/tests/dummy_app/server/async-startup.tests.js b/tests/dummy_app/server/async-startup.tests.js
new file mode 100644
index 0000000..04fee7b
--- /dev/null
+++ b/tests/dummy_app/server/async-startup.tests.js
@@ -0,0 +1,21 @@
+/* eslint-env mocha */
+import { Meteor } from 'meteor/meteor';
+import assert from 'assert';
+
+// Simulate async startup work (e.g. ensuring MongoDB indices, initializing
+// collections). Without the fix in server.js, mocha.run() can fire before
+// this callback completes, causing the test below to fail.
+let startupCompleted = false;
+
+Meteor.startup(async () => {
+  await new Promise(resolve => setTimeout(resolve, 50));
+  startupCompleted = true;
+});
+
+describe('async Meteor.startup()', function () {
+  it('should complete before tests run', function () {
+    assert.strictEqual(startupCompleted, true,
+      'Async Meteor.startup() callback did not complete before tests ran. ' +
+      'See https://github.com/Meteor-Community-Packages/meteor-mocha/issues/176');
+  });
+});