diff --git a/runtime/bin/dart_embedder_api_impl.cc b/runtime/bin/dart_embedder_api_impl.cc
index 92081c694d9..c280fc8e2df 100644
--- a/runtime/bin/dart_embedder_api_impl.cc
+++ b/runtime/bin/dart_embedder_api_impl.cc
@@ -6,6 +6,7 @@
 
 #include "bin/dartutils.h"
 #include "bin/eventhandler.h"
+#include "bin/io_service.h"
 #include "bin/isolate_data.h"
 #include "bin/process.h"
 #include "bin/secure_socket_filter.h"
@@ -54,6 +55,7 @@ void Cleanup() {
   bin::SSLFilter::Cleanup();
 #endif
   bin::Process::Cleanup();
+  bin::IOService::Cleanup();
 }
 
 Dart_Isolate CreateKernelServiceIsolate(const IsolateCreationData& data,
diff --git a/runtime/bin/io_service.cc b/runtime/bin/io_service.cc
index 673a0cee1f1..0afa15ef1b1 100644
--- a/runtime/bin/io_service.cc
+++ b/runtime/bin/io_service.cc
@@ -55,10 +55,22 @@ void IOServiceCallback(Dart_Port dest_port_id, Dart_CObject* message) {
 }
 
 intptr_t IOService::max_concurrency_ = 32;
+std::atomic<Dart_Port> IOService::port_ = ILLEGAL_PORT;
 
 Dart_Port IOService::GetServicePort() {
-  return Dart_NewConcurrentNativePort("IOService", IOServiceCallback,
-                                      max_concurrency_);
+  Dart_Port port = port_;
+  if (port == ILLEGAL_PORT) {
+    port = Dart_NewConcurrentNativePort("IOService", IOServiceCallback,
+                                        max_concurrency_);
+    Dart_Port expected = ILLEGAL_PORT;
+    if (!port_.compare_exchange_strong(expected, port)) {
+      // Lost the initialization race. Use the winner's port and close our port.
+      // The winner's port is eventually implicitly closed by VM shutdown.
+      Dart_CloseNativePort(port);
+      return expected;
+    }
+  }
+  return port;
 }
 
 void FUNCTION_NAME(IOService_NewServicePort)(Dart_NativeArguments args) {
diff --git a/runtime/bin/io_service.h b/runtime/bin/io_service.h
index d440f0f738f..5e92251a113 100644
--- a/runtime/bin/io_service.h
+++ b/runtime/bin/io_service.h
@@ -9,6 +9,8 @@
 #error "io_service.h can only be included on builds with IO and SSL enabled"
 #endif
 
+#include <atomic>
+
 #include "bin/builtin.h"
 #include "bin/utils.h"
 
@@ -69,12 +71,14 @@ class IOService {
   enum { IO_SERVICE_REQUEST_LIST(DECLARE_REQUEST) };
 
   static Dart_Port GetServicePort();
+  static void Cleanup() { port_ = ILLEGAL_PORT; }
 
   static intptr_t max_concurrency() { return max_concurrency_; }
   static void set_max_concurrency(intptr_t value) { max_concurrency_ = value; }
 
  private:
   static intptr_t max_concurrency_;
+  static std::atomic<Dart_Port> port_;
 
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(IOService);
diff --git a/tests/standalone/io/leak_io_service_test.dart b/tests/standalone/io/leak_io_service_test.dart
new file mode 100644
index 00000000000..0c3a2c57948
--- /dev/null
+++ b/tests/standalone/io/leak_io_service_test.dart
@@ -0,0 +1,28 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import "dart:async";
+import "dart:io";
+import "dart:isolate";
+
+child(replyPort) async {
+  var ops = <Future>[];
+  for (var i = 0; i < 32; i++) {
+    ops.add(File(Platform.executable).stat()); // Uses the IO Service.
+  }
+  await Future.wait(ops);
+  replyPort.send(null);
+}
+
+main() {
+  var pending = 1000;
+  var port = new RawReceivePort();
+  port.handler = (_) {
+    pending--;
+    if (pending == 0) port.close();
+  };
+  for (var i = 0; i < pending; i++) {
+    Isolate.spawn(child, port.sendPort);
+  }
+}