diff --git a/lms/djangoapps/course_home_api/outline/tests/test_view.py b/lms/djangoapps/course_home_api/outline/tests/test_view.py
index e9a3570ea6bd..acfe86ca8ed8 100644
--- a/lms/djangoapps/course_home_api/outline/tests/test_view.py
+++ b/lms/djangoapps/course_home_api/outline/tests/test_view.py
@@ -10,6 +10,7 @@
 import ddt
 from completion.models import BlockCompletion
 from django.conf import settings
+from django.contrib.auth.models import AnonymousUser
 from django.test import override_settings
 from django.urls import reverse
 from edx_toggles.toggles.testutils import override_waffle_flag
@@ -20,6 +21,7 @@
 from common.djangoapps.student.models import CourseEnrollment
 from common.djangoapps.student.roles import CourseInstructorRole
 from common.djangoapps.student.tests.factories import UserFactory
+from lms.djangoapps.course_home_api.outline.views import CourseNavigationBlocksView
 from lms.djangoapps.course_home_api.tests.utils import BaseCourseHomeTests
 from lms.djangoapps.course_home_api.toggles import COURSE_HOME_SEND_COURSE_PROGRESS_ANALYTICS_FOR_STUDENT
 from lms.djangoapps.grades.course_grade_factory import CourseGradeFactory
@@ -584,6 +586,20 @@ def test_get_unauthenticated_user(self):
         assert response.status_code == 200
         assert response.data.get('blocks') is None
 
+    def test_anonymous_user_completion_dict_does_not_lookup_completions(self):
+        """
+        Test that anonymous users do not query completion data.
+        """
+        view = CourseNavigationBlocksView()
+        view.request = Mock(user=AnonymousUser())
+        view.kwargs = {'course_key_string': str(self.course.id)}
+
+        with patch('lms.djangoapps.course_home_api.outline.views.BlockCompletion.objects.filter') as mock_filter:
+            completions = view.completions_dict
+
+        assert completions == {}
+        mock_filter.assert_not_called()
+
     def test_course_staff_can_see_non_user_specific_content_in_masquerade(self):
         """
         Test that course staff can see the outline and other non-user-specific content when masquerading as a learner
diff --git a/lms/djangoapps/course_home_api/outline/views.py b/lms/djangoapps/course_home_api/outline/views.py
index 0c62d8a34921..b9168c6ca5fa 100644
--- a/lms/djangoapps/course_home_api/outline/views.py
+++ b/lms/djangoapps/course_home_api/outline/views.py
@@ -613,6 +613,11 @@ def completions_dict(self):
         Dictionary keys are block keys and values are int values
         representing the completion status of the block.
         """
+        # Anonymous users have no completion rows; return empty data to avoid
+        # querying BlockCompletion with AnonymousUser for public course navigation.
+        if self.request.user.is_anonymous:
+            return {}
+
         course_key_string = self.kwargs.get('course_key_string')
         course_key = CourseKey.from_string(course_key_string)
         completions = BlockCompletion.objects.filter(user=self.request.user, context_key=course_key).values_list(