diff --git a/lms/djangoapps/instructor/tests/views/test_instructor_dashboard.py b/lms/djangoapps/instructor/tests/views/test_instructor_dashboard.py
index 37b2224c8d..c3de2244fb 100644
--- a/lms/djangoapps/instructor/tests/views/test_instructor_dashboard.py
+++ b/lms/djangoapps/instructor/tests/views/test_instructor_dashboard.py
@@ -330,7 +330,8 @@ class TestInstructorDashboard(ModuleStoreTestCase, LoginEnrollmentTestCase, XssT
     )
     def test_staff_can_see_writable_gradebook(self):
         """
-        Test that, when the writable gradebook featue is enabled, a staff member can see it.
+        Test that, when the writable gradebook feature is enabled and
+        deployed in another domain, a staff member can see it.
         """
         waffle_flag = waffle_flags()[WRITABLE_GRADEBOOK]
         with override_waffle_flag(waffle_flag, active=True):
@@ -345,6 +346,28 @@ class TestInstructorDashboard(ModuleStoreTestCase, LoginEnrollmentTestCase, XssT
         'of enrolled learners.'
     )
 
+    @patch(
+        'lms.djangoapps.instructor.views.instructor_dashboard.settings.WRITABLE_GRADEBOOK_URL',
+        settings.LMS_ROOT_URL + '/gradebook'
+    )
+    def test_staff_can_see_writable_gradebook_as_subdirectory(self):
+        """
+        Test that, when the writable gradebook feature is enabled and
+        deployed in a subdirectory, a staff member can see it.
+        """
+        waffle_flag = waffle_flags()[WRITABLE_GRADEBOOK]
+        with override_waffle_flag(waffle_flag, active=True):
+            response = self.client.get(self.url)
+
+        expected_gradebook_url = '{}/{}'.format(settings.WRITABLE_GRADEBOOK_URL, self.course.id)
+        self.assertContains(response, expected_gradebook_url)
+        self.assertContains(response, 'View Gradebook')
+
+    GRADEBOOK_LEARNER_COUNT_MESSAGE = (
+        'Note: This feature is available only to courses with a small number ' +
+        'of enrolled learners.'
+    )
+
     def test_gradebook_learner_count_message(self):
         """
         Test that, when the writable gradebook featue is NOT enabled, there IS
diff --git a/lms/djangoapps/instructor/views/instructor_dashboard.py b/lms/djangoapps/instructor/views/instructor_dashboard.py
index 1cf944bd51..b75acb4d06 100644
--- a/lms/djangoapps/instructor/views/instructor_dashboard.py
+++ b/lms/djangoapps/instructor/views/instructor_dashboard.py
@@ -573,7 +573,7 @@ def _section_student_admin(course, access):
         'spoc_gradebook_url': reverse('spoc_gradebook', kwargs={'course_id': six.text_type(course_key)}),
     }
     if is_writable_gradebook_enabled(course_key) and settings.WRITABLE_GRADEBOOK_URL:
-        section_data['writable_gradebook_url'] = urljoin(settings.WRITABLE_GRADEBOOK_URL, '/' + text_type(course_key))
+        section_data['writable_gradebook_url'] = '{}/{}'.format(settings.WRITABLE_GRADEBOOK_URL, text_type(course_key))
     return section_data