@@ -16,6 +16,7 @@ const {
   createNativeKeyObjectClass,
   // eslint-disable-next-line no-restricted-syntax -- intended here
   getKeyObjectSlots: nativeGetKeyObjectSlots,
+  isKeyObject: isNativeKeyObject,
   createCryptoKeyClass,
   // eslint-disable-next-line no-restricted-syntax -- intended here
   getCryptoKeySlots: nativeGetCryptoKeySlots,
@@ -120,6 +121,7 @@ for (const m of [[kKeyEncodingPKCS1, 'pkcs1'], [kKeyEncodingPKCS8, 'pkcs8'],
 // slot tuple in a private field so no forgeable own Symbols are exposed on
 // public KeyObject instances.
 let getKeyObjectSlots; // Populated by the createNativeKeyObjectClass callback.
+let isKeyObject;
 
 const kKeyObjectSlotType = 0;
 const kKeyObjectSlotHandle = 1;
@@ -225,6 +227,10 @@ const {
     }
 
     static {
+      isKeyObject = (key) => {
+        if (key == null || typeof key !== 'object') return false;
+        return #slots in key || isNativeKeyObject(key);
+      };
       getKeyObjectSlots = (key) => {
         if (!key || typeof key !== 'object')
           throw new ERR_INVALID_THIS('KeyObject');
@@ -1044,18 +1050,6 @@ function getKeyObjectAsymmetricKeyDetails(key) {
   return cached;
 }
 
-function isKeyObject(obj) {
-  if (obj == null || typeof obj !== 'object')
-    return false;
-
-  try {
-    getKeyObjectSlots(obj);
-    return true;
-  } catch {
-    return false;
-  }
-}
-
 // CryptoKey is a plain JS class whose prototype's [[Prototype]] is
 // Object.prototype, as Web Crypto requires. Instance storage (type enum,
 // extractable, algorithm, usages mask, and the KeyObject handle) lives
 
@@ -1695,12 +1695,15 @@ void NativeKeyObject::Initialize(Environment* env, Local<Object> target) {
             NativeKeyObject::CreateNativeKeyObjectClass);
   SetMethod(
       env->context(), target, "getKeyObjectSlots", NativeKeyObject::GetSlots);
+  SetMethodNoSideEffect(
+      env->context(), target, "isKeyObject", NativeKeyObject::IsKeyObject);
 }
 
 void NativeKeyObject::RegisterExternalReferences(
     ExternalReferenceRegistry* registry) {
   registry->Register(NativeKeyObject::CreateNativeKeyObjectClass);
   registry->Register(NativeKeyObject::GetSlots);
+  registry->Register(NativeKeyObject::IsKeyObject);
   registry->Register(NativeKeyObject::New);
 }
 
@@ -1709,6 +1712,12 @@ bool NativeKeyObject::HasInstance(Environment* env, Local<Value> value) {
   return !t.IsEmpty() && t->HasInstance(value);
 }
 
+void NativeKeyObject::IsKeyObject(const FunctionCallbackInfo<Value>& args) {
+  Environment* env = Environment::GetCurrent(args);
+  CHECK_EQ(args.Length(), 1);
+  args.GetReturnValue().Set(HasInstance(env, args[0]));
+}
+
 void NativeKeyObject::New(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
   CHECK_EQ(args.Length(), 1);
 
@@ -209,6 +209,7 @@ class NativeKeyObject : public BaseObject {
   static void New(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void CreateNativeKeyObjectClass(
       const v8::FunctionCallbackInfo<v8::Value>& args);
+  static void IsKeyObject(const v8::FunctionCallbackInfo<v8::Value>& args);
 
   // True if `value` is a real NativeKeyObject instance. Uses the
   // FunctionTemplate stored on the Environment as a brand check.
 
@@ -949,6 +949,7 @@ export interface CryptoBinding {
   getFipsCrypto(): 0 | 1;
   getFipsCryptoGeneration(): bigint;
   getHashes(): string[];
+  isKeyObject(key: unknown): boolean;
   getKeyObjectSlots(key: object): InternalCryptoBinding.KeyObjectSlots;
   getOpenSSLSecLevelCrypto(): number | undefined;
   getSSLCiphers(): string[];