diff --git a/vmware_nsx/plugins/nsx_v3/plugin.py b/vmware_nsx/plugins/nsx_v3/plugin.py
index 941386ecbd..46f55c721d 100644
--- a/vmware_nsx/plugins/nsx_v3/plugin.py
+++ b/vmware_nsx/plugins/nsx_v3/plugin.py
@@ -1465,12 +1465,16 @@ class NsxV3Plugin(addr_pair_db.AllowedAddressPairsMixin,
             port = self._get_port(context, port_id)
             if port.get('fixed_ips'):
                 subnet_id = port['fixed_ips'][0]['subnet_id']
+                self._confirm_router_interface_not_in_use(
+                    context, router_id, subnet_id)
             if not (port['device_owner'] in const.ROUTER_INTERFACE_OWNERS
                     and port['device_id'] == router_id):
                 raise l3.RouterInterfaceNotFound(router_id=router_id,
                                                  port_id=port_id)
         elif 'subnet_id' in interface_info:
             subnet_id = interface_info['subnet_id']
+            self._confirm_router_interface_not_in_use(
+                context, router_id, subnet_id)
             subnet = self._get_subnet(context, subnet_id)
             rport_qry = context.session.query(models_v2.Port)
             ports = rport_qry.filter_by(
diff --git a/vmware_nsx/tests/unit/nsx_v3/test_plugin.py b/vmware_nsx/tests/unit/nsx_v3/test_plugin.py
index bdae850602..228b92cab1 100644
--- a/vmware_nsx/tests/unit/nsx_v3/test_plugin.py
+++ b/vmware_nsx/tests/unit/nsx_v3/test_plugin.py
@@ -14,6 +14,7 @@
 # limitations under the License.
 import mock
 import six
+from webob import exc
 
 from neutron.api.v2 import attributes
 from neutron.common import constants
@@ -380,6 +381,39 @@ class TestL3NatTestCase(L3NatTest,
                 self._router_interface_action('remove', r1['router']['id'],
                                               s1['subnet']['id'], None)
 
+    def test_router_remove_interface_inuse_return_409(self):
+        with self.router() as r1,\
+                self.subnet() as ext_subnet,\
+                self.subnet(cidr='11.0.0.0/24') as s1:
+            self._set_net_external(ext_subnet['subnet']['network_id'])
+            self._router_interface_action(
+                'add', r1['router']['id'],
+                s1['subnet']['id'], None)
+            self._add_external_gateway_to_router(
+                r1['router']['id'],
+                ext_subnet['subnet']['network_id'])
+            with self.port(subnet=s1,) as p:
+                fip_res = self._create_floatingip(
+                    self.fmt,
+                    ext_subnet['subnet']['network_id'],
+                    subnet_id=ext_subnet['subnet']['id'],
+                    port_id=p['port']['id'])
+                fip = self.deserialize(self.fmt, fip_res)
+                self._router_interface_action(
+                    'remove',
+                    r1['router']['id'],
+                    s1['subnet']['id'],
+                    None,
+                    expected_code=exc.HTTPConflict.code)
+                self._delete('floatingips', fip['floatingip']['id'])
+            self._remove_external_gateway_from_router(
+                r1['router']['id'],
+                ext_subnet['subnet']['network_id'])
+            self._router_interface_action('remove',
+                                          r1['router']['id'],
+                                          s1['subnet']['id'],
+                                          None)
+
     def test_router_update_on_external_port(self):
         with self.router() as r:
             with self.subnet(cidr='10.0.1.0/24') as s: