diff --git a/Sources/XCTest/Public/Asynchronous/XCTestCase+Asynchronous.swift b/Sources/XCTest/Public/Asynchronous/XCTestCase+Asynchronous.swift
index 7b122532..b9935ff7 100644
--- a/Sources/XCTest/Public/Asynchronous/XCTestCase+Asynchronous.swift
+++ b/Sources/XCTest/Public/Asynchronous/XCTestCase+Asynchronous.swift
@@ -41,7 +41,7 @@ public extension XCTestCase {
     ///   these environments. To ensure compatibility of tests between
     ///   swift-corelibs-xctest and Apple XCTest, it is not recommended to pass
     ///   explicit values for `file` and `line`.
-    // FIXME: This should have `@MainActor` to match Xcode XCTest, but adding it causes errors in tests authored pre-Swift Concurrency which don't typically have `@MainActor`.
+    @preconcurrency @MainActor
     func waitForExpectations(timeout: TimeInterval, file: StaticString = #file, line: Int = #line, handler: XCWaitCompletionHandler? = nil) {
         precondition(Thread.isMainThread, "\(#function) must be called on the main thread")
         if currentWaiter != nil {
diff --git a/Sources/XCTest/Public/XCTestCase.swift b/Sources/XCTest/Public/XCTestCase.swift
index aadfecc7..4d734cd8 100644
--- a/Sources/XCTest/Public/XCTestCase.swift
+++ b/Sources/XCTest/Public/XCTestCase.swift
@@ -48,7 +48,7 @@ open class XCTestCase: XCTest {
         return 1
     }
 
-    // FIXME: Once `waitForExpectations(timeout:...handler:)` gains `@MainActor`, this may be able to add it as well.
+    @MainActor
     internal var currentWaiter: XCTWaiter?
 
     /// The set of expectations made upon this test case.
diff --git a/Tests/Functional/Asynchronous/Expectations/main.swift b/Tests/Functional/Asynchronous/Expectations/main.swift
index 6ebb3352..8d0b1599 100644
--- a/Tests/Functional/Asynchronous/Expectations/main.swift
+++ b/Tests/Functional/Asynchronous/Expectations/main.swift
@@ -551,6 +551,28 @@ class ExpectationsTestCase: XCTestCase {
         RunLoop.main.run(until: Date() + 1)
     }
 
+// CHECK: Test Case 'ExpectationsTestCase.test_waitForExpectationsAsync' started at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
+// CHECK: Test Case 'ExpectationsTestCase.test_waitForExpectationsAsync' passed \(\d+\.\d+ seconds\)
+    func test_waitForExpectationsAsync() async {
+        // Basic check that waitForExpectations() is functional when used with the
+        // await keyword in an async function.
+        let expectation = self.expectation(description: "foo")
+        expectation.fulfill()
+        await self.waitForExpectations(timeout: 0.0)
+    }
+
+// CHECK: Test Case 'ExpectationsTestCase.test_waitForExpectationsFromMainActor' started at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
+// CHECK: Test Case 'ExpectationsTestCase.test_waitForExpectationsFromMainActor' passed \(\d+\.\d+ seconds\)
+    func test_waitForExpectationsFromMainActor() async {
+        await MainActor.run {
+            // Basic check that waitForExpectations() is functional and does not need
+            // the await keyword when used from a main-actor-isolated test function.
+            let expectation = self.expectation(description: "foo")
+            expectation.fulfill()
+            self.waitForExpectations(timeout: 0.0)
+        }
+    }
+
     static var allTests = {
         return [
             ("test_waitingForAnUnfulfilledExpectation_fails", test_waitingForAnUnfulfilledExpectation_fails),
@@ -603,15 +625,19 @@ class ExpectationsTestCase: XCTestCase {
             ("test_expectationCreationOnSecondaryThread", test_expectationCreationOnSecondaryThread),
             ("test_expectationCreationWhileWaiting", test_expectationCreationWhileWaiting),
             ("test_runLoopInsideDispatch", test_runLoopInsideDispatch),
+
+            // waitForExpectations() + @MainActor
+            ("test_waitForExpectationsAsync", asyncTest(test_waitForExpectationsAsync)),
+            ("test_waitForExpectationsFromMainActor", asyncTest(test_waitForExpectationsFromMainActor)),
         ]
     }()
 }
 // CHECK: Test Suite 'ExpectationsTestCase' failed at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
-// CHECK: \t Executed 35 tests, with 16 failures \(2 unexpected\) in \d+\.\d+ \(\d+\.\d+\) seconds
+// CHECK: \t Executed 37 tests, with 16 failures \(2 unexpected\) in \d+\.\d+ \(\d+\.\d+\) seconds
 
 XCTMain([testCase(ExpectationsTestCase.allTests)])
 
 // CHECK: Test Suite '.*\.xctest' failed at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
-// CHECK: \t Executed 35 tests, with 16 failures \(2 unexpected\) in \d+\.\d+ \(\d+\.\d+\) seconds
+// CHECK: \t Executed 37 tests, with 16 failures \(2 unexpected\) in \d+\.\d+ \(\d+\.\d+\) seconds
 // CHECK: Test Suite 'All tests' failed at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
-// CHECK: \t Executed 35 tests, with 16 failures \(2 unexpected\) in \d+\.\d+ \(\d+\.\d+\) seconds
+// CHECK: \t Executed 37 tests, with 16 failures \(2 unexpected\) in \d+\.\d+ \(\d+\.\d+\) seconds