diff --git a/scrapy/utils/request.py b/scrapy/utils/request.py
index 398403d90..20f93c1aa 100644
--- a/scrapy/utils/request.py
+++ b/scrapy/utils/request.py
@@ -204,7 +204,10 @@ def request_to_curl(request: Request) -> str:
     cookies = ""
     if request.cookies:
         if isinstance(request.cookies, dict):
-            cookie = "; ".join(f"{k}={v}" for k, v in request.cookies.items())
+            cookie = "; ".join(
+                f"{_cookie_value_to_unicode(k)}={_cookie_value_to_unicode(v)}"
+                for k, v in request.cookies.items()
+            )
             cookies = f"--cookie '{cookie}'"
         elif isinstance(request.cookies, list):
             cookie = "; ".join(
diff --git a/tests/test_utils_request.py b/tests/test_utils_request.py
index e4967d4e7..f9b6a4d81 100644
--- a/tests/test_utils_request.py
+++ b/tests/test_utils_request.py
@@ -401,6 +401,19 @@ class TestRequestToCurl:
         )
         self._test_request(request_object, expected_curl_command)
 
+    def test_cookies_dict_bytes(self):
+        request_object = Request(
+            "https://www.httpbin.org/post",
+            method="POST",
+            cookies={b"foo": b"bar"},
+            body=json.dumps({"foo": "bar"}),
+        )
+        expected_curl_command = (
+            "curl -X POST https://www.httpbin.org/post"
+            " --data-raw '{\"foo\": \"bar\"}' --cookie 'foo=bar'"
+        )
+        self._test_request(request_object, expected_curl_command)
+
     def test_cookies_list(self):
         request_object = Request(
             "https://www.httpbin.org/post",