diff --git a/netbox/extras/api/customfields.py b/netbox/extras/api/customfields.py
index 0497138c4..d17b988c9 100644
--- a/netbox/extras/api/customfields.py
+++ b/netbox/extras/api/customfields.py
@@ -103,6 +103,9 @@ class CustomFieldModelSerializer(ValidatedModelSerializer):
             for cfv in instance.custom_field_values.all():
                 if cfv.field.type == CF_TYPE_SELECT:
                     custom_fields[cfv.field.name] = CustomFieldChoiceSerializer(cfv.value).data
+                elif cfv.field.type == CF_TYPE_DATE:
+                    # convert datetime object to str
+                    custom_fields[cfv.field.name] = str(cfv.value)
                 else:
                     custom_fields[cfv.field.name] = cfv.value
             instance.custom_fields = custom_fields
diff --git a/netbox/extras/tests/test_customfields.py b/netbox/extras/tests/test_customfields.py
index 805ee5543..8b5aaedf5 100644
--- a/netbox/extras/tests/test_customfields.py
+++ b/netbox/extras/tests/test_customfields.py
@@ -177,7 +177,7 @@ class CustomFieldAPITest(HttpStatusMixin, APITestCase):
             (self.cf_text, 'Test string'),
             (self.cf_integer, 1234),
             (self.cf_boolean, True),
-            (self.cf_date, date(2016, 6, 23)),
+            (self.cf_date, "2016-06-23"),
             (self.cf_url, 'http://example.com/'),
             (self.cf_select, self.cf_select_choice1.pk),
         ]