diff --git a/django/core/checks/urls.py b/django/core/checks/urls.py
index c39010fb7d..13c7e2b08b 100644
--- a/django/core/checks/urls.py
+++ b/django/core/checks/urls.py
@@ -50,17 +50,18 @@ def check_url_namespaces_unique(app_configs, **kwargs):
     return errors
 
 
-def _load_all_namespaces(resolver):
+def _load_all_namespaces(resolver, parents=()):
     """
     Recursively load all namespaces from URL patterns.
     """
     url_patterns = getattr(resolver, 'url_patterns', [])
     namespaces = [
-        url.namespace for url in url_patterns
+        ':'.join(parents + (url.namespace,)) for url in url_patterns
         if getattr(url, 'namespace', None) is not None
     ]
     for pattern in url_patterns:
-        namespaces.extend(_load_all_namespaces(pattern))
+        current = parents + (getattr(pattern, 'namespace', ()),)
+        namespaces.extend(_load_all_namespaces(pattern, current))
     return namespaces
 
 
diff --git a/tests/check_framework/urls/unique_namespaces.py b/tests/check_framework/urls/unique_namespaces.py
index 897f27757e..10d427eec9 100644
--- a/tests/check_framework/urls/unique_namespaces.py
+++ b/tests/check_framework/urls/unique_namespaces.py
@@ -5,7 +5,14 @@ common_url_patterns = ([
     url(r'^app-url/', include([])),
 ], 'common')
 
+nested_url_patterns = ([
+    url(r'^common/', include(common_url_patterns, namespace='nested')),
+], 'nested')
+
 urlpatterns = [
     url(r'^app-ns1-0/', include(common_url_patterns, namespace='app-include-1')),
-    url(r'^app-ns1-1/', include(common_url_patterns, namespace='app-include-2'))
+    url(r'^app-ns1-1/', include(common_url_patterns, namespace='app-include-2')),
+    # 'nested' is included twice but namespaced by nested-1 and nested-2.
+    url(r'^app-ns1-2/', include(nested_url_patterns, namespace='nested-1')),
+    url(r'^app-ns1-3/', include(nested_url_patterns, namespace='nested-2')),
 ]