diff --git a/pkg/analyzer/lib/error/error.dart b/pkg/analyzer/lib/error/error.dart
index c77e160..d02d937 100644
--- a/pkg/analyzer/lib/error/error.dart
+++ b/pkg/analyzer/lib/error/error.dart
@@ -610,6 +610,7 @@
   HintCode.UNUSED_RESULT,
   HintCode.UNUSED_RESULT_WITH_MESSAGE,
   HintCode.UNUSED_SHOWN_NAME,
+  HintCode.USE_OF_NATIVE_EXTENSION,
   LanguageCode.IMPLICIT_DYNAMIC_FIELD,
   LanguageCode.IMPLICIT_DYNAMIC_FUNCTION,
   LanguageCode.IMPLICIT_DYNAMIC_INVOKE,
diff --git a/pkg/analyzer/lib/src/dart/error/hint_codes.dart b/pkg/analyzer/lib/src/dart/error/hint_codes.dart
index a4a3347..cb5d4eb 100644
--- a/pkg/analyzer/lib/src/dart/error/hint_codes.dart
+++ b/pkg/analyzer/lib/src/dart/error/hint_codes.dart
@@ -3197,6 +3197,15 @@
       hasPublishedDocs: true);
 
   /**
+   * Users should not import or export Dart native extensions via 'dart-ext:'.
+   */
+  static const HintCode USE_OF_NATIVE_EXTENSION = HintCode(
+      'USE_OF_NATIVE_EXTENSION',
+      "Dart native extensions are deprecated and will not be available in Dart "
+          "2.15",
+      correction: "Try using dart:ffi for C interop.");
+
+  /**
    * Initialize a newly created error code to have the given [name]. The message
    * associated with the error will be created from the given [message]
    * template. The correction associated with the error will be created from the
diff --git a/pkg/analyzer/lib/src/error/best_practices_verifier.dart b/pkg/analyzer/lib/src/error/best_practices_verifier.dart
index b03f8b8..329f055 100644
--- a/pkg/analyzer/lib/src/error/best_practices_verifier.dart
+++ b/pkg/analyzer/lib/src/error/best_practices_verifier.dart
@@ -368,6 +368,7 @@
   void visitExportDirective(ExportDirective node) {
     _deprecatedVerifier.exportDirective(node);
     _checkForInternalExport(node);
+    _checkForUseOfNativeExtension(node);
     super.visitExportDirective(node);
   }
 
@@ -521,6 +522,7 @@
     }
     _invalidAccessVerifier.verifyImport(node);
     _checkForImportOfLegacyLibraryIntoNullSafe(node);
+    _checkForUseOfNativeExtension(node);
     super.visitImportDirective(node);
   }
 
@@ -1389,6 +1391,16 @@
     return false;
   }
 
+  void _checkForUseOfNativeExtension(UriBasedDirective node) {
+    var uri = node.uriContent;
+    if (uri == null) {
+      return;
+    }
+    if (uri.startsWith('dart-ext:')) {
+      _errorReporter.reportErrorForNode(HintCode.USE_OF_NATIVE_EXTENSION, node);
+    }
+  }
+
   void _checkRequiredParameter(FormalParameterList node) {
     final requiredParameters =
         node.parameters.where((p) => p.declaredElement?.hasRequired == true);
diff --git a/pkg/analyzer/test/generated/non_error_resolver_test.dart b/pkg/analyzer/test/generated/non_error_resolver_test.dart
index 402d7cc..702e0c2 100644
--- a/pkg/analyzer/test/generated/non_error_resolver_test.dart
+++ b/pkg/analyzer/test/generated/non_error_resolver_test.dart
@@ -2421,15 +2421,18 @@
   const factory Foo.foo() native 'Foo_Foo_foo';
 }
 ''', [
+      error(HintCode.USE_OF_NATIVE_EXTENSION, 0, 20),
       error(ParserErrorCode.CONST_CONSTRUCTOR_WITH_BODY, 47, 6),
     ]);
   }
 
   test_nativeFunctionBodyInNonSDKCode_function() async {
-    await assertNoErrorsInCode(r'''
+    await assertErrorsInCode(r'''
 import 'dart-ext:x';
 int m(a) native 'string';
-''');
+''', [
+      error(HintCode.USE_OF_NATIVE_EXTENSION, 0, 20),
+    ]);
   }
 
   test_newWithAbstractClass_factory() async {
diff --git a/pkg/analyzer/test/src/diagnostics/test_all.dart b/pkg/analyzer/test/src/diagnostics/test_all.dart
index 5be1286..c6fcbe0 100644
--- a/pkg/analyzer/test/src/diagnostics/test_all.dart
+++ b/pkg/analyzer/test/src/diagnostics/test_all.dart
@@ -243,7 +243,7 @@
     as import_deferred_library_with_load_function;
 import 'import_internal_library_test.dart' as import_internal_library;
 import 'import_of_legacy_library_into_null_safe_test.dart'
-    as mport_of_legacy_library_into_null_safe;
+    as import_of_legacy_library_into_null_safe;
 import 'import_of_non_library_test.dart' as import_of_non_library;
 import 'inconsistent_case_expression_types_test.dart'
     as inconsistent_case_expression_types;
@@ -669,6 +669,7 @@
 import 'unused_shown_name_test.dart' as unused_shown_name;
 import 'uri_does_not_exist_test.dart' as uri_does_not_exist;
 import 'uri_with_interpolation_test.dart' as uri_with_interpolation;
+import 'use_of_native_extension_test.dart' as use_of_native_extension;
 import 'use_of_nullable_value_test.dart' as use_of_nullable_value_test;
 import 'use_of_void_result_test.dart' as use_of_void_result;
 import 'variable_type_mismatch_test.dart' as variable_type_mismatch;
@@ -848,7 +849,7 @@
     implicit_this_reference_in_initializer.main();
     import_deferred_library_with_load_function.main();
     import_internal_library.main();
-    mport_of_legacy_library_into_null_safe.main();
+    import_of_legacy_library_into_null_safe.main();
     import_of_non_library.main();
     inconsistent_case_expression_types.main();
     inconsistent_inheritance_getter_and_method.main();
@@ -1139,6 +1140,7 @@
     unused_shown_name.main();
     uri_does_not_exist.main();
     uri_with_interpolation.main();
+    use_of_native_extension.main();
     use_of_nullable_value_test.main();
     use_of_void_result.main();
     variable_type_mismatch.main();
diff --git a/pkg/analyzer/test/src/diagnostics/uri_does_not_exist_test.dart b/pkg/analyzer/test/src/diagnostics/uri_does_not_exist_test.dart
index a9bdb9b..4ae834a 100644
--- a/pkg/analyzer/test/src/diagnostics/uri_does_not_exist_test.dart
+++ b/pkg/analyzer/test/src/diagnostics/uri_does_not_exist_test.dart
@@ -91,22 +91,28 @@
 
   test_valid_dll() async {
     newFile("$testPackageLibPath/lib.dll");
-    await assertNoErrorsInCode('''
+    await assertErrorsInCode('''
 import 'dart-ext:lib';
-''');
+''', [
+      error(HintCode.USE_OF_NATIVE_EXTENSION, 0, 22),
+    ]);
   }
 
   test_valid_dylib() async {
     newFile("$testPackageLibPath/lib.dylib");
-    await assertNoErrorsInCode('''
+    await assertErrorsInCode('''
 import 'dart-ext:lib';
-''');
+''', [
+      error(HintCode.USE_OF_NATIVE_EXTENSION, 0, 22),
+    ]);
   }
 
   test_valid_so() async {
     newFile("$testPackageLibPath/lib.so");
-    await assertNoErrorsInCode('''
+    await assertErrorsInCode('''
 import 'dart-ext:lib';
-''');
+''', [
+      error(HintCode.USE_OF_NATIVE_EXTENSION, 0, 22),
+    ]);
   }
 }
diff --git a/pkg/analyzer/test/src/diagnostics/use_of_native_extension_test.dart b/pkg/analyzer/test/src/diagnostics/use_of_native_extension_test.dart
new file mode 100644
index 0000000..e172765
--- /dev/null
+++ b/pkg/analyzer/test/src/diagnostics/use_of_native_extension_test.dart
@@ -0,0 +1,35 @@
+// Copyright (c) 2021, 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 'package:analyzer/src/error/codes.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import '../dart/resolution/context_collection_resolution.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(UseOfNativeExtensionTest);
+  });
+}
+
+@reflectiveTest
+class UseOfNativeExtensionTest extends PubPackageResolutionTest {
+  test_export() async {
+    await assertErrorsInCode(r'''
+export 'dart-ext:x';
+''', [
+      error(HintCode.USE_OF_NATIVE_EXTENSION, 0, 20),
+      error(CompileTimeErrorCode.URI_DOES_NOT_EXIST, 7, 12),
+    ]);
+  }
+
+  test_import() async {
+    await assertErrorsInCode(r'''
+import 'dart-ext:x';
+''', [
+      // TODO(srawlins): Why does this file not have a URI_DOES_NOT_EXIST error?
+      error(HintCode.USE_OF_NATIVE_EXTENSION, 0, 20),
+    ]);
+  }
+}
diff --git a/tools/VERSION b/tools/VERSION
index 9e20aca..7e30d67 100644
--- a/tools/VERSION
+++ b/tools/VERSION
@@ -27,5 +27,5 @@
 MAJOR 2
 MINOR 14
 PATCH 0
-PRERELEASE 135
+PRERELEASE 136
 PRERELEASE_PATCH 0
\ No newline at end of file