diff --git a/aodh/api/controllers/v2/alarm_rules/gnocchi.py b/aodh/api/controllers/v2/alarm_rules/gnocchi.py
index 6576fc2bf..25663d2a0 100644
--- a/aodh/api/controllers/v2/alarm_rules/gnocchi.py
+++ b/aodh/api/controllers/v2/alarm_rules/gnocchi.py
@@ -18,6 +18,8 @@ import threading
 import cachetools
 from gnocchiclient import client
 from gnocchiclient import exceptions
+from keystoneauth1 import exceptions as ka_exceptions
+from oslo_config import cfg
 from oslo_serialization import jsonutils
 import pecan
 import wsme
@@ -28,6 +30,14 @@ from aodh.api.controllers.v2 import utils as v2_utils
 from aodh import keystone_client
 
 
+GNOCCHI_OPTS = [
+    cfg.StrOpt('gnocchi_external_project_owner',
+               default="service",
+               help='Project name of resources creator in Gnocchi. '
+               '(For example the Ceilometer project name'),
+]
+
+
 class GnocchiUnavailable(Exception):
     code = 503
 
@@ -122,6 +132,20 @@ class AggregationMetricByResourcesLookupRule(AlarmGnocchiThresholdRule):
                                        'resource_type'])
         return rule
 
+    cache = cachetools.TTLCache(maxsize=1, ttl=3600)
+    lock = threading.RLock()
+
+    @staticmethod
+    @cachetools.cached(cache, lock=lock)
+    def get_external_project_owner():
+        kc = keystone_client.get_client(pecan.request.cfg)
+        project_name = pecan.request.cfg.api.gnocchi_external_project_owner
+        try:
+            project = kc.projects.find(name=project_name)
+            return project.id
+        except ka_exceptions.NotFound:
+            return None
+
     @classmethod
     def validate_alarm(cls, alarm):
         super(AggregationMetricByResourcesLookupRule,
@@ -135,14 +159,27 @@ class AggregationMetricByResourcesLookupRule(AlarmGnocchiThresholdRule):
         except ValueError:
             raise wsme.exc.InvalidInput('rule/query', rule.query)
 
+        conf = pecan.request.cfg
+
         # Scope the alarm to the project id if needed
         auth_project = v2_utils.get_auth_project(alarm.project_id)
         if auth_project:
-            query = {"and": [{"=": {"created_by_project_id": auth_project}},
-                             query]}
+
+            perms_filter = {"=": {"created_by_project_id": auth_project}}
+
+            external_project_owner = cls.get_external_project_owner()
+            if external_project_owner:
+                perms_filter = {"or": [
+                    perms_filter,
+                    {"and": [
+                        {"=": {"created_by_project_id":
+                               external_project_owner}},
+                        {"=": {"project_id": auth_project}}]}
+                ]}
+
+            query = {"and": [perms_filter, query]}
             rule.query = jsonutils.dumps(query)
 
-        conf = pecan.request.cfg
         gnocchi_client = client.Client(
             '1', keystone_client.get_session(conf),
             interface=conf.service_credentials.interface,
diff --git a/aodh/opts.py b/aodh/opts.py
index dbc02f2d1..2f434e6fd 100644
--- a/aodh/opts.py
+++ b/aodh/opts.py
@@ -16,6 +16,7 @@ import itertools
 from keystoneauth1 import loading
 
 import aodh.api
+import aodh.api.controllers.v2.alarm_rules.gnocchi
 import aodh.api.controllers.v2.alarms
 import aodh.coordination
 import aodh.evaluator
@@ -42,6 +43,7 @@ def list_opts():
         ('api',
          itertools.chain(
              aodh.api.OPTS,
+             aodh.api.controllers.v2.alarm_rules.gnocchi.GNOCCHI_OPTS,
              aodh.api.controllers.v2.alarms.ALARM_API_OPTS)),
         ('coordination', aodh.coordination.OPTS),
         ('database', aodh.storage.OPTS),
diff --git a/aodh/tests/functional/api/v2/test_alarm_scenarios.py b/aodh/tests/functional/api/v2/test_alarm_scenarios.py
index d89dd894b..9b801d7b1 100644
--- a/aodh/tests/functional/api/v2/test_alarm_scenarios.py
+++ b/aodh/tests/functional/api/v2/test_alarm_scenarios.py
@@ -2607,7 +2607,9 @@ class TestAlarmsRuleGnocchi(TestAlarmsBase):
         self.assertEqual(1, len(alarms))
         self._verify_alarm(json, alarms[0])
 
-    def test_post_gnocchi_aggregation_alarm_project_constraint(self):
+    @mock.patch('aodh.keystone_client.get_client')
+    def test_post_gnocchi_aggregation_alarm_project_constraint(self,
+                                                               get_client):
         json = {
             'enabled': False,
             'name': 'project_constraint',
@@ -2630,10 +2632,21 @@ class TestAlarmsRuleGnocchi(TestAlarmsBase):
             }
         }
 
-        expected_query = {"and": [{"=": {"created_by_project_id":
-                                         self.auth_headers['X-Project-Id']}},
-                                  {"=": {"server_group":
-                                         "my_autoscaling_group"}}]}
+        expected_query = {"and": [
+            {"or": [
+                {"=": {"created_by_project_id":
+                       self.auth_headers['X-Project-Id']}},
+                {"and": [
+                    {"=": {"created_by_project_id": "<my-uuid>"}},
+                    {"=": {"project_id": self.auth_headers['X-Project-Id']}}
+                ]},
+            ]},
+            {"=": {"server_group": "my_autoscaling_group"}},
+        ]}
+
+        ks_client = mock.Mock()
+        ks_client.projects.find.return_value = mock.Mock(id='<my-uuid>')
+        get_client.return_value = ks_client
 
         with mock.patch('aodh.api.controllers.v2.alarm_rules.'
                         'gnocchi.client') as clientlib:
diff --git a/releasenotes/notes/gnocchi-external-resource-owner-3fad253d30746b0d.yaml b/releasenotes/notes/gnocchi-external-resource-owner-3fad253d30746b0d.yaml
new file mode 100644
index 000000000..45a2997a3
--- /dev/null
+++ b/releasenotes/notes/gnocchi-external-resource-owner-3fad253d30746b0d.yaml
@@ -0,0 +1,11 @@
+---
+fixes:
+  - |
+    When an unprivileged user want to access to Gnocchi resources created by
+    Ceilometer, that doesn't work because the filter scope the Gnocchi query to
+    resource owner to the user. To fix we introduce a new configuration option
+    "gnocchi_external_project_owner" set by default to "service". The new
+    filter now allow two kind of Gnocchi resources:
+    * owned by the user project
+    * owned by "gnocchi_external_project_owner" and the orignal project_id of
+      the resource is the user project.