diff --git a/zaqar/storage/errors.py b/zaqar/storage/errors.py
index 21f88bbce..4e0560336 100644
--- a/zaqar/storage/errors.py
+++ b/zaqar/storage/errors.py
@@ -191,3 +191,8 @@ class PoolCapabilitiesMismatch(ExceptionBase):
 
     msg_format = (u'The pool being added does not '
                   u'support the minimum set of capabilities')
+
+
+class PoolAlreadyExists(Conflict):
+
+    msg_format = u'The database URI is in use by another pool.'
diff --git a/zaqar/storage/mongodb/pools.py b/zaqar/storage/mongodb/pools.py
index d2b39188a..31aa687ae 100644
--- a/zaqar/storage/mongodb/pools.py
+++ b/zaqar/storage/mongodb/pools.py
@@ -23,6 +23,7 @@ Schema:
 """
 
 import functools
+from pymongo import errors as mongo_error
 
 from zaqar.common import utils as common_utils
 from zaqar.storage import base
@@ -97,13 +98,16 @@ class PoolsController(base.PoolsBase):
     @utils.raises_conn_error
     def _create(self, name, weight, uri, group=None, options=None):
         options = {} if options is None else options
-        self._col.update({'n': name},
-                         {'$set': {'n': name,
-                                   'w': weight,
-                                   'u': uri,
-                                   'g': group,
-                                   'o': options}},
-                         upsert=True)
+        try:
+            self._col.update({'n': name},
+                             {'$set': {'n': name,
+                                       'w': weight,
+                                       'u': uri,
+                                       'g': group,
+                                       'o': options}},
+                             upsert=True)
+        except mongo_error.DuplicateKeyError:
+            raise errors.PoolAlreadyExists()
 
     @utils.raises_conn_error
     def _exists(self, name):
diff --git a/zaqar/tests/unit/storage/test_impl_mongodb.py b/zaqar/tests/unit/storage/test_impl_mongodb.py
index 2064e4cdb..cb340d6d4 100644
--- a/zaqar/tests/unit/storage/test_impl_mongodb.py
+++ b/zaqar/tests/unit/storage/test_impl_mongodb.py
@@ -528,6 +528,13 @@ class MongodbPoolsTests(base.PoolsControllerTest):
                                          group=self.pool_group,
                                          options={})
 
+    def test_duplicate_uri(self):
+        with testing.expect(errors.PoolAlreadyExists):
+            # The url 'localhost' is used in setUp(). So reusing the uri
+            # 'localhost' here will raise PoolAlreadyExists.
+            self.pools_controller.create(str(uuid.uuid1()), 100, 'localhost',
+                                         group=str(uuid.uuid1()), options={})
+
 
 @testing.requires_mongodb
 class MongodbCatalogueTests(base.CatalogueControllerTest):
diff --git a/zaqar/transport/wsgi/v1_0/pools.py b/zaqar/transport/wsgi/v1_0/pools.py
index d97f0eb52..54e15a5a2 100644
--- a/zaqar/transport/wsgi/v1_0/pools.py
+++ b/zaqar/transport/wsgi/v1_0/pools.py
@@ -38,9 +38,11 @@ registered, there is an optional field::
 import falcon
 import jsonschema
 from oslo_log import log
+import six
 
 from zaqar.common.api.schemas import pools as schema
 from zaqar.common import utils as common_utils
+from zaqar.i18n import _
 from zaqar.storage import errors
 from zaqar.storage import utils as storage_utils
 from zaqar.transport import utils as transport_utils
@@ -171,11 +173,16 @@ class Resource(object):
             raise wsgi_errors.HTTPBadRequestBody(
                 'cannot connect to %s' % data['uri']
             )
-        self._ctrl.create(pool, weight=data['weight'],
-                          uri=data['uri'],
-                          options=data.get('options', {}))
-        response.status = falcon.HTTP_201
-        response.location = request.path
+        try:
+            self._ctrl.create(pool, weight=data['weight'],
+                              uri=data['uri'],
+                              options=data.get('options', {}))
+            response.status = falcon.HTTP_201
+            response.location = request.path
+        except errors.PoolAlreadyExists as e:
+            LOG.exception(e)
+            title = _(u'Unable to create pool')
+            raise falcon.HTTPConflict(title, six.text_type(e))
 
     def on_delete(self, request, response, project_id, pool):
         """Deregisters a pool.
diff --git a/zaqar/transport/wsgi/v1_1/pools.py b/zaqar/transport/wsgi/v1_1/pools.py
index a830a844b..5c37b5370 100644
--- a/zaqar/transport/wsgi/v1_1/pools.py
+++ b/zaqar/transport/wsgi/v1_1/pools.py
@@ -186,6 +186,10 @@ class Resource(object):
             LOG.exception(e)
             title = _(u'Unable to create pool')
             raise falcon.HTTPBadRequest(title, six.text_type(e))
+        except errors.PoolAlreadyExists as e:
+            LOG.exception(e)
+            title = _(u'Unable to create pool')
+            raise falcon.HTTPConflict(title, six.text_type(e))
 
     def on_delete(self, request, response, project_id, pool):
         """Deregisters a pool.
diff --git a/zaqar/transport/wsgi/v2_0/pools.py b/zaqar/transport/wsgi/v2_0/pools.py
index a2d3848fd..131b0750e 100644
--- a/zaqar/transport/wsgi/v2_0/pools.py
+++ b/zaqar/transport/wsgi/v2_0/pools.py
@@ -190,6 +190,10 @@ class Resource(object):
             LOG.exception(e)
             title = _(u'Unable to create pool')
             raise falcon.HTTPBadRequest(title, six.text_type(e))
+        except errors.PoolAlreadyExists as e:
+            LOG.exception(e)
+            title = _(u'Unable to create pool')
+            raise falcon.HTTPConflict(title, six.text_type(e))
 
     @acl.enforce("pools:delete")
     def on_delete(self, request, response, project_id, pool):