diff --git a/django/core/handlers/wsgi.py b/django/core/handlers/wsgi.py
index c3d359caf72..7f6d37b3c11 100644
--- a/django/core/handlers/wsgi.py
+++ b/django/core/handlers/wsgi.py
@@ -136,7 +136,8 @@ class WSGIRequest(http.HttpRequest):
     def _get_get(self):
         if not hasattr(self, '_get'):
             # The WSGI spec says 'QUERY_STRING' may be absent.
-            self._get = http.QueryDict(self.environ.get('QUERY_STRING', ''), encoding=self._encoding)
+            raw_query_string = get_bytes_from_wsgi(self.environ, 'QUERY_STRING', '')
+            self._get = http.QueryDict(raw_query_string, encoding=self._encoding)
         return self._get
 
     def _set_get(self, get):
@@ -152,7 +153,8 @@ class WSGIRequest(http.HttpRequest):
 
     def _get_cookies(self):
         if not hasattr(self, '_cookies'):
-            self._cookies = http.parse_cookie(self.environ.get('HTTP_COOKIE', ''))
+            raw_cookie = get_str_from_wsgi(self.environ, 'HTTP_COOKIE', '')
+            self._cookies = http.parse_cookie(raw_cookie)
         return self._cookies
 
     def _set_cookies(self, cookies):
@@ -265,3 +267,15 @@ def get_bytes_from_wsgi(environ, key, default):
     # decoded with ISO-8859-1. This is wrong for Django websites where UTF-8
     # is the default. Re-encode to recover the original bytestring.
     return value if six.PY2 else value.encode(ISO_8859_1)
+
+
+def get_str_from_wsgi(environ, key, default):
+    """
+    Get a value from the WSGI environ dictionary as bytes.
+
+    key and default should be str objects. Under Python 2 they may also be
+    unicode objects provided they only contain ASCII characters.
+    """
+    value = environ.get(str(key), str(default))
+    # Same comment as above
+    return value if six.PY2 else value.encode(ISO_8859_1).decode(UTF_8)
diff --git a/tests/handlers/tests.py b/tests/handlers/tests.py
index 2f9f304b81a..9d47b0b0835 100644
--- a/tests/handlers/tests.py
+++ b/tests/handlers/tests.py
@@ -1,8 +1,11 @@
-from django.core.handlers.wsgi import WSGIHandler
+from __future__ import unicode_literals
+
+from django.core.handlers.wsgi import WSGIHandler, WSGIRequest
 from django.core.signals import request_started, request_finished
 from django.db import close_old_connections, connection
 from django.test import RequestFactory, TestCase, TransactionTestCase
 from django.test.utils import override_settings
+from django.utils import six
 
 
 class HandlerTests(TestCase):
@@ -30,11 +33,19 @@ class HandlerTests(TestCase):
     def test_bad_path_info(self):
         """Tests for bug #15672 ('request' referenced before assignment)"""
         environ = RequestFactory().get('/').environ
-        environ['PATH_INFO'] = '\xed'
+        environ['PATH_INFO'] = b'\xed' if six.PY2 else '\xed'
         handler = WSGIHandler()
         response = handler(environ, lambda *a, **k: None)
         self.assertEqual(response.status_code, 400)
 
+    def test_non_ascii_cookie(self):
+        """Test that non-ASCII cookies set in JavaScript are properly decoded (#20557)."""
+        environ = RequestFactory().get('/').environ
+        raw_cookie = 'want="café"'.encode('utf-8')
+        environ['HTTP_COOKIE'] = raw_cookie if six.PY2 else raw_cookie.decode('iso-8859-1')
+        request = WSGIRequest(environ)
+        self.assertEqual(request.COOKIES['want'], "café")
+
 
 class TransactionsPerRequestTests(TransactionTestCase):