diff --git a/plugins/cookie_manager/CHANGELOG.md b/plugins/cookie_manager/CHANGELOG.md
index 5c8f50138..11ec9141d 100644
--- a/plugins/cookie_manager/CHANGELOG.md
+++ b/plugins/cookie_manager/CHANGELOG.md
@@ -2,7 +2,7 @@
 
 ## Unreleased
 
-*None.*
+- Fix duplicate cookies when requests are retried with the same `RequestOptions`.
 
 ## 3.4.0
 
diff --git a/plugins/cookie_manager/lib/src/cookie_mgr.dart b/plugins/cookie_manager/lib/src/cookie_mgr.dart
index a3a79d17a..650027e6f 100644
--- a/plugins/cookie_manager/lib/src/cookie_mgr.dart
+++ b/plugins/cookie_manager/lib/src/cookie_mgr.dart
@@ -149,12 +149,20 @@ class CookieManager extends Interceptor {
     final savedCookies = await cookieJar.loadForRequest(options.uri);
     final previousCookies =
         options.headers[HttpHeaders.cookieHeader] as String?;
+    // Per RFC 6265 Section 4.2, the Cookie header carries only name=value
+    // pairs without domain or path. The saved cookies are already scoped
+    // to the request URI by cookieJar.loadForRequest, so matching by name
+    // is sufficient to detect duplicates from a retried request.
+    final savedCookieNames = savedCookies.map((c) => c.name).toSet();
+    final previousList = previousCookies
+        ?.split(';')
+        .where((e) => e.isNotEmpty)
+        .map((c) => _fromSetCookieValue(c))
+        .whereType<Cookie>() // Use .nonNulls when the minimum SDK is 3.0.
+        .where((c) => !savedCookieNames.contains(c.name))
+        .toList();
     final cookies = getCookies([
-      ...?previousCookies
-          ?.split(';')
-          .where((e) => e.isNotEmpty)
-          .map((c) => _fromSetCookieValue(c))
-          .whereType<Cookie>(), // Use .nonNulls when the minimum SDK is 3.0.
+      ...?previousList,
       ...savedCookies,
     ]);
     return cookies;
diff --git a/plugins/cookie_manager/test/cookies_test.dart b/plugins/cookie_manager/test/cookies_test.dart
index b01f8ea41..ca1427883 100644
--- a/plugins/cookie_manager/test/cookies_test.dart
+++ b/plugins/cookie_manager/test/cookies_test.dart
@@ -228,6 +228,77 @@ void main() {
     });
   });
 
+  test('no duplicate cookies on retry', () async {
+    const List<String> mockResponseCookies = [
+      'a=1; Path=/',
+      'b=2; Path=/',
+    ];
+    const exampleUrl = 'https://example.com';
+
+    final cookieJar = CookieJar();
+    final cookieManager = CookieManager(cookieJar);
+
+    // Save cookies from a response.
+    final requestOptions = RequestOptions(baseUrl: exampleUrl);
+    final mockResponse = Response(
+      requestOptions: requestOptions,
+      headers: Headers.fromMap(
+        {HttpHeaders.setCookieHeader: mockResponseCookies},
+      ),
+    );
+    await cookieManager.onResponse(
+      mockResponse,
+      MockResponseInterceptorHandler(),
+    );
+
+    // First request sets cookie header.
+    final firstOptions = RequestOptions(baseUrl: exampleUrl);
+    final firstHandler = MockRequestInterceptorHandler('a=1; b=2');
+    await cookieManager.onRequest(firstOptions, firstHandler);
+
+    // Simulate retry: onRequest is called again on the same RequestOptions
+    // which already has the cookie header from the first attempt.
+    final retryHandler = MockRequestInterceptorHandler('a=1; b=2');
+    await cookieManager.onRequest(firstOptions, retryHandler);
+  });
+
+  test('same-name cookies with different paths are preserved on retry',
+      () async {
+    // RFC 6265 Section 5.3: cookies are identified by (name, domain, path).
+    // Two cookies with the same name but different paths must both be kept.
+    const List<String> mockResponseCookies = [
+      'session=abc; Path=/',
+      'session=xyz; Path=/api',
+    ];
+    const exampleUrl = 'https://example.com/api/endpoint';
+
+    final cookieJar = CookieJar();
+    final cookieManager = CookieManager(cookieJar);
+
+    final requestOptions = RequestOptions(baseUrl: exampleUrl);
+    final mockResponse = Response(
+      requestOptions: requestOptions,
+      headers: Headers.fromMap(
+        {HttpHeaders.setCookieHeader: mockResponseCookies},
+      ),
+    );
+    await cookieManager.onResponse(
+      mockResponse,
+      MockResponseInterceptorHandler(),
+    );
+
+    // First request: both cookies should be sent.
+    final firstOptions = RequestOptions(baseUrl: exampleUrl);
+    final firstHandler =
+        MockRequestInterceptorHandler('session=xyz; session=abc');
+    await cookieManager.onRequest(firstOptions, firstHandler);
+
+    // Retry: same cookies, no duplicates.
+    final retryHandler =
+        MockRequestInterceptorHandler('session=xyz; session=abc');
+    await cookieManager.onRequest(firstOptions, retryHandler);
+  });
+
   test('cookies replacement', () async {
     final cookies = [
       Cookie('foo', 'bar')..path = '/',