diff --git a/lib/src/validator.dart b/lib/src/validator.dart
index 4336d4a08..5a03d7b71 100644
--- a/lib/src/validator.dart
+++ b/lib/src/validator.dart
@@ -19,6 +19,7 @@ import 'validator/dependency_override.dart';
 import 'validator/deprecated_fields.dart';
 import 'validator/directory.dart';
 import 'validator/executable.dart';
+import 'validator/file_case.dart';
 import 'validator/flutter_constraint.dart';
 import 'validator/flutter_plugin_format.dart';
 import 'validator/gitignore.dart';
@@ -136,6 +137,7 @@ abstract class Validator {
     required List<String> errors,
   }) async {
     var validators = [
+      FileCaseValidator(),
       AnalyzeValidator(),
       GitignoreValidator(),
       PubspecValidator(),
diff --git a/lib/src/validator/file_case.dart b/lib/src/validator/file_case.dart
new file mode 100644
index 000000000..ad73d47e7
--- /dev/null
+++ b/lib/src/validator/file_case.dart
@@ -0,0 +1,32 @@
+// Copyright (c) 2023, 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 'package:collection/collection.dart';
+
+import '../validator.dart';
+
+/// Validates that a package files all are unique even after case-normalization.
+class FileCaseValidator extends Validator {
+  @override
+  Future validate() async {
+    final lowerCaseToFile = <String, String>{};
+    for (final file in files.sorted()) {
+      final lowerCase = file.toLowerCase();
+      final existing = lowerCaseToFile[lowerCase];
+      if (existing != null) {
+        errors.add('''
+The file $file and $existing only differ in capitalization.
+
+This is not supported across platforms.
+
+Try renaming one of them.
+''');
+        break;
+      }
+      lowerCaseToFile[lowerCase] = file;
+    }
+  }
+}
diff --git a/test/validator/file_case_test.dart b/test/validator/file_case_test.dart
new file mode 100644
index 000000000..67d820039
--- /dev/null
+++ b/test/validator/file_case_test.dart
@@ -0,0 +1,42 @@
+// Copyright (c) 2023, 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.
+
+// These tests only work on case-sensitive file systems (ie. only on linux).
+@OnPlatform({
+  'windows': Skip('Windows file system is case-insensitive'),
+  'mac-os': Skip('MacOS file system is case-insensitive')
+})
+
+import 'package:pub/src/exit_codes.dart';
+import 'package:test/test.dart';
+
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+
+Future<void> expectValidation(error, int exitCode) async {
+  await runPub(
+    error: error,
+    args: ['publish', '--dry-run'],
+    workingDirectory: d.path(appPath),
+    exitCode: exitCode,
+  );
+}
+
+late d.DirectoryDescriptor fakeFlutterRoot;
+
+void main() {
+  test('Recognizes files that only differ in capitalization.', () async {
+    await d.validPackage.create();
+    await d.dir(appPath, [d.file('Pubspec.yaml')]).create();
+    await expectValidation(
+      allOf(
+        contains('Package validation found the following error:'),
+        contains(
+          'The file ./pubspec.yaml and ./Pubspec.yaml only differ in capitalization.',
+        ),
+      ),
+      DATA,
+    );
+  });
+}