diff --git a/neutron/db/securitygroups_db.py b/neutron/db/securitygroups_db.py
index 16d04aceaa7..95f354d74d8 100644
--- a/neutron/db/securitygroups_db.py
+++ b/neutron/db/securitygroups_db.py
@@ -22,6 +22,7 @@ from neutron_lib.callbacks import resources
 from neutron_lib import constants
 from neutron_lib import context as context_lib
 from neutron_lib import exceptions as n_exc
+from neutron_lib.objects import exceptions as obj_exc
 from neutron_lib.utils import helpers
 from neutron_lib.utils import net
 from oslo_utils import uuidutils
@@ -41,6 +42,9 @@ from neutron.objects import base as base_obj
 from neutron.objects import securitygroup as sg_obj
 
 
+DEFAULT_SG_DESCRIPTION = _('Default security group')
+
+
 @resource_extend.has_resource_extenders
 @registry.has_registry_receivers
 class SecurityGroupDbMixin(ext_sg.SecurityGroupPluginBase):
@@ -805,10 +809,13 @@ class SecurityGroupDbMixin(ext_sg.SecurityGroupPluginBase):
             'security_group':
                 {'name': 'default',
                  'tenant_id': tenant_id,
-                 'description': _('Default security group')}
+                 'description': DEFAULT_SG_DESCRIPTION}
         }
-        return self.create_security_group(context, security_group,
-                                          default_sg=True)['id']
+        try:
+            return self.create_security_group(context, security_group,
+                                              default_sg=True)['id']
+        except obj_exc.NeutronDbObjectDuplicateEntry:
+            return self._get_default_sg_id(context, tenant_id)
 
     def _get_security_groups_on_port(self, context, port):
         """Check that all security groups on port belong to tenant.
diff --git a/neutron/tests/unit/db/test_securitygroups_db.py b/neutron/tests/unit/db/test_securitygroups_db.py
index 92b2f0259e7..f0bfdf38b63 100644
--- a/neutron/tests/unit/db/test_securitygroups_db.py
+++ b/neutron/tests/unit/db/test_securitygroups_db.py
@@ -20,6 +20,7 @@ from neutron_lib.callbacks import registry
 from neutron_lib.callbacks import resources
 from neutron_lib import constants
 from neutron_lib import context
+from neutron_lib.objects import exceptions as obj_exc
 import sqlalchemy
 import testtools
 
@@ -517,3 +518,49 @@ class SecurityGroupDbMixinTestCase(testlib_api.SqlTestCase):
         for rule in (rule for rule in rules_after if rule not in rules_before):
             self.assertEqual('tenant_1', rule['tenant_id'])
             self.assertEqual(self.sg_user['id'], rule['security_group_id'])
+
+    def test__ensure_default_security_group(self):
+        with mock.patch.object(
+                self.mixin, '_get_default_sg_id') as get_default_sg_id,\
+                mock.patch.object(
+                        self.mixin, 'create_security_group') as create_sg:
+            get_default_sg_id.return_value = None
+            self.mixin._ensure_default_security_group(self.ctx, 'tenant_1')
+            create_sg.assert_called_once_with(
+                self.ctx,
+                {'security_group': {
+                    'name': 'default',
+                    'tenant_id': 'tenant_1',
+                    'description': securitygroups_db.DEFAULT_SG_DESCRIPTION}},
+                default_sg=True)
+            get_default_sg_id.assert_called_once_with(self.ctx, 'tenant_1')
+
+    def test__ensure_default_security_group_already_exists(self):
+        with mock.patch.object(
+                self.mixin, '_get_default_sg_id') as get_default_sg_id,\
+                mock.patch.object(
+                        self.mixin, 'create_security_group') as create_sg:
+            get_default_sg_id.return_value = 'default_sg_id'
+            self.mixin._ensure_default_security_group(self.ctx, 'tenant_1')
+            create_sg.assert_not_called()
+            get_default_sg_id.assert_called_once_with(self.ctx, 'tenant_1')
+
+    def test__ensure_default_security_group_created_in_parallel(self):
+        with mock.patch.object(
+                self.mixin, '_get_default_sg_id') as get_default_sg_id,\
+                mock.patch.object(
+                        self.mixin, 'create_security_group') as create_sg:
+            get_default_sg_id.side_effect = [None, 'default_sg_id']
+            create_sg.side_effect = obj_exc.NeutronDbObjectDuplicateEntry(
+                mock.Mock(), mock.Mock())
+            self.mixin._ensure_default_security_group(self.ctx, 'tenant_1')
+            create_sg.assert_called_once_with(
+                self.ctx,
+                {'security_group': {
+                    'name': 'default',
+                    'tenant_id': 'tenant_1',
+                    'description': securitygroups_db.DEFAULT_SG_DESCRIPTION}},
+                default_sg=True)
+            get_default_sg_id.assert_has_calls([
+                mock.call(self.ctx, 'tenant_1'),
+                mock.call(self.ctx, 'tenant_1')])