diff --git a/neutron_fwaas/services/firewall/fwaas_plugin.py b/neutron_fwaas/services/firewall/fwaas_plugin.py
index 50f4e6f2d..53358e837 100644
--- a/neutron_fwaas/services/firewall/fwaas_plugin.py
+++ b/neutron_fwaas/services/firewall/fwaas_plugin.py
@@ -22,7 +22,7 @@ from oslo_config import cfg
 from oslo_log import log as logging
 import oslo_messaging
 
-from neutron_fwaas._i18n import _LW
+from neutron_fwaas._i18n import _LI, _LW
 from neutron_fwaas.common import fwaas_constants as f_const
 from neutron_fwaas.db.firewall import firewall_db
 from neutron_fwaas.db.firewall import firewall_router_insertion_db
@@ -60,18 +60,22 @@ class FirewallCallbacks(object):
     def firewall_deleted(self, context, firewall_id, **kwargs):
         """Agent uses this to indicate firewall is deleted."""
         LOG.debug("firewall_deleted() called")
-        with context.session.begin(subtransactions=True):
-            fw_db = self.plugin._get_firewall(context, firewall_id)
-            # allow to delete firewalls in ERROR state
-            if fw_db.status in (n_const.PENDING_DELETE, n_const.ERROR):
-                self.plugin.delete_db_firewall_object(context, firewall_id)
-                return True
-            else:
-                LOG.warning(_LW('Firewall %(fw)s unexpectedly deleted by '
-                                'agent, status was %(status)s'),
-                            {'fw': firewall_id, 'status': fw_db.status})
-                fw_db.update({"status": n_const.ERROR})
-                return False
+        try:
+            with context.session.begin(subtransactions=True):
+                fw_db = self.plugin._get_firewall(context, firewall_id)
+                # allow to delete firewalls in ERROR state
+                if fw_db.status in (n_const.PENDING_DELETE, n_const.ERROR):
+                    self.plugin.delete_db_firewall_object(context, firewall_id)
+                    return True
+                else:
+                    LOG.warning(_LW('Firewall %(fw)s unexpectedly deleted by '
+                                    'agent, status was %(status)s'),
+                                {'fw': firewall_id, 'status': fw_db.status})
+                    fw_db.update({"status": n_const.ERROR})
+                    return False
+        except fw_ext.FirewallNotFound:
+            LOG.info(_LI('Firewall %s already deleted'), firewall_id)
+            return True
 
     def get_firewalls_for_tenant(self, context, **kwargs):
         """Agent uses this to get all firewalls and rules for a tenant."""
diff --git a/neutron_fwaas/tests/unit/services/firewall/test_fwaas_plugin.py b/neutron_fwaas/tests/unit/services/firewall/test_fwaas_plugin.py
index 9671776da..4ac227fdc 100644
--- a/neutron_fwaas/tests/unit/services/firewall/test_fwaas_plugin.py
+++ b/neutron_fwaas/tests/unit/services/firewall/test_fwaas_plugin.py
@@ -195,6 +195,47 @@ class TestFirewallCallbacks(TestFirewallRouterInsertionBase):
                                       self.plugin.get_firewall,
                                       ctx, fw_id)
 
+    def test_firewall_deleted_concurrently(self):
+        ctx = context.get_admin_context()
+        alt_ctx = context.get_admin_context()
+
+        _get_firewall = self.plugin._get_firewall
+
+        def getdelete(context, firewall_id):
+            fw_db = _get_firewall(context, firewall_id)
+            # NOTE(cby): Use a different session to simulate a concurrent del
+            self.plugin.delete_db_firewall_object(alt_ctx, firewall_id)
+            return fw_db
+
+        with self.firewall_policy() as fwp:
+            fwp_id = fwp['firewall_policy']['id']
+            with self.firewall(
+                firewall_policy_id=fwp_id,
+                admin_state_up=test_db_firewall.ADMIN_STATE_UP,
+                do_delete=False
+            ) as fw:
+                fw_id = fw['firewall']['id']
+                with ctx.session.begin(subtransactions=True):
+                    fw_db = self.plugin._get_firewall(ctx, fw_id)
+                    fw_db['status'] = const.PENDING_DELETE
+                    ctx.session.flush()
+
+                with mock.patch.object(
+                    self.plugin, '_get_firewall', side_effect=getdelete
+                ):
+                    observed = self.callbacks.firewall_deleted(
+                        ctx, fw_id, host='dummy')
+                    self.assertTrue(observed)
+
+                self.assertRaises(firewall.FirewallNotFound,
+                                  self.plugin.get_firewall,
+                                  ctx, fw_id)
+
+    def test_firewall_deleted_not_found(self):
+        ctx = context.get_admin_context()
+        observed = self.callbacks.firewall_deleted(ctx, 'notfound', host='hh')
+        self.assertTrue(observed)
+
     def test_firewall_deleted_error(self):
         ctx = context.get_admin_context()
         with self.firewall_policy() as fwp: