diff --git a/pymongo/common.py b/pymongo/common.py
index a62114ad1..bf5919d84 100644
--- a/pymongo/common.py
+++ b/pymongo/common.py
@@ -336,7 +336,8 @@ VALIDATORS = {
     'gssapiservicename': validate_basestring,
     'authmechanismproperties': validate_auth_mechanism_properties,
     'uuidrepresentation': validate_uuid_representation,
-    'socketkeepalive': validate_boolean
+    'socketkeepalive': validate_boolean,
+    'maxpoolsize': validate_positive_integer_or_none
 }
 
 
diff --git a/pymongo/mongo_client.py b/pymongo/mongo_client.py
index 439757a41..41b3a8004 100644
--- a/pymongo/mongo_client.py
+++ b/pymongo/mongo_client.py
@@ -140,6 +140,8 @@ class MongoClient(common.BaseObject):
 
           | **Other optional parameters can be passed as keyword arguments:**
 
+          - `maxPoolSize` (optional): Alias for max_pool_size. Takes
+            precedence over max_pool_size.
           - `socketTimeoutMS`: (integer or None) How long (in milliseconds) a
             send or receive on a socket can take before timing out. Defaults to
             ``None`` (no timeout).
@@ -312,8 +314,10 @@ class MongoClient(common.BaseObject):
         options['codec_options'] = CodecOptions(
             document_class, tz_aware, uuid_representation)
 
-        self.__max_pool_size = common.validate_positive_integer_or_none(
-            'max_pool_size', max_pool_size)
+        self.__max_pool_size = options.get(
+            'maxpoolsize',
+            common.validate_positive_integer_or_none('max_pool_size',
+                                                     max_pool_size))
 
         self.__cursor_manager = CursorManager(self)
 
diff --git a/pymongo/mongo_replica_set_client.py b/pymongo/mongo_replica_set_client.py
index e09cf850e..32be49edd 100644
--- a/pymongo/mongo_replica_set_client.py
+++ b/pymongo/mongo_replica_set_client.py
@@ -490,6 +490,8 @@ class MongoReplicaSetClient(common.BaseObject):
             precedence.
           - `port`: For compatibility with :class:`~mongo_client.MongoClient`.
             The default port number to use for hosts.
+          - `maxpoolsize` (optional): Alias for max_pool_size. Takes
+            precendence over max_pool_size.
           - `socketTimeoutMS`: (integer or None) How long (in milliseconds) a
             send or receive on a socket can take before timing out. Defaults to
             ``None`` (no timeout).
@@ -595,8 +597,6 @@ class MongoReplicaSetClient(common.BaseObject):
         self.__index_cache = {}
         self.__auth_credentials = {}
 
-        self.__max_pool_size = common.validate_positive_integer_or_none(
-            'max_pool_size', max_pool_size)
         self.__monitor = None
         self.__closed = False
 
@@ -633,6 +633,11 @@ class MongoReplicaSetClient(common.BaseObject):
             self.__opts[option] = value
         self.__opts.update(options)
 
+        self.__max_pool_size = self.__opts.get(
+            'maxpoolsize',
+            common.validate_positive_integer_or_none('max_pool_size',
+                                                     max_pool_size))
+
         common.validate_boolean('tz_aware', tz_aware)
         uuid_representation = options.pop('uuidrepresentation', PYTHON_LEGACY)
         self.__opts['codec_options'] = CodecOptions(
diff --git a/test/test_client.py b/test/test_client.py
index 6a2548f11..2f4f2fe2a 100644
--- a/test/test_client.py
+++ b/test/test_client.py
@@ -331,6 +331,31 @@ class TestClient(unittest.TestCase, TestRequestMixin):
         finally:
             ctx.exit()
 
+    def test_backport_maxpoolsize_uri(self):
+        uri = "mongodb://%s:%s" % (host, port)
+        mps_uri = ("mongodb://%s:%d/?maxPoolSize=10" % (host, port))
+
+        client = MongoClient(uri)
+        self.assertEqual(client.max_pool_size, 100)
+
+        client = MongoClient(uri, maxPoolSize=10)
+        self.assertEqual(client.max_pool_size, 10)
+
+        client = MongoClient(uri, max_pool_size=8, maxPoolSize=10)
+        self.assertEqual(client.max_pool_size, 10)
+
+        client = MongoClient(mps_uri)
+        self.assertEqual(client.max_pool_size, 10)
+
+        client = MongoClient(mps_uri, maxPoolSize=8)
+        self.assertEqual(client.max_pool_size, 10)
+
+        client = MongoClient(mps_uri, max_pool_size=8)
+        self.assertEqual(client.max_pool_size, 10)
+
+        client = MongoClient(mps_uri, max_pool_size=6, maxPoolSize=8)
+        self.assertEqual(client.max_pool_size, 10)
+
     def test_backport_localthresholdms_uri(self):
         uri = "mongodb://%s:%s" % (host, port)
         lt_uri = "mongodb://%s:%d/?localThresholdMS=10" % (host, port)
diff --git a/test/test_pooling_base.py b/test/test_pooling_base.py
index d47f01134..f84c37409 100644
--- a/test/test_pooling_base.py
+++ b/test/test_pooling_base.py
@@ -402,6 +402,20 @@ class _TestPooling(_TestPoolingBase):
         c = MongoClient(host=host, port=port, max_pool_size=100)
         self.assertEqual(c.max_pool_size, 100)
 
+    def test_maxpoolsize_validation(self):
+        self.assertRaises(
+            ConfigurationError, MongoClient, host=host, port=port,
+            maxpoolsize=-1
+        )
+
+        self.assertRaises(
+            ConfigurationError, MongoClient, host=host, port=port,
+            maxpoolsize='foo'
+        )
+
+        c = MongoClient(host=host, port=port, maxpoolsize=100)
+        self.assertEqual(c.max_pool_size, 100)
+
     def test_no_disconnect(self):
         run_cases(self, [NoRequest, NonUnique, Unique, SaveAndFind])
 
diff --git a/test/test_replica_set_client.py b/test/test_replica_set_client.py
index 02e1017fb..cb63fd78e 100644
--- a/test/test_replica_set_client.py
+++ b/test/test_replica_set_client.py
@@ -692,6 +692,12 @@ class TestReplicaSetClient(TestReplicaSetClientBase, TestRequestMixin):
         self.assertEqual(pool.wait_queue_multiple, 2)
         self.assertEqual(pool._socket_semaphore.waiter_semaphore.counter, 6)
 
+    def test_waitQueueMultiple_backport_maxpoolsize(self):
+        client = self._get_client(maxpoolsize=3, waitQueueMultiple=2)
+        pool = get_pool(client)
+        self.assertEqual(pool.wait_queue_multiple, 2)
+        self.assertEqual(pool._socket_semaphore.waiter_semaphore.counter, 6)
+
     def test_socketKeepAlive(self):
         client = self._get_client(socketKeepAlive=True)
         pool = get_pool(client)
@@ -743,6 +749,32 @@ class TestReplicaSetClient(TestReplicaSetClientBase, TestRequestMixin):
         self.assertTrue("pymongo_test_bernie" in dbs)
         client.close()
 
+    def test_backport_repl_maxpoolsize_uri(self):
+        uri = "mongodb://%s/?replicaSet=%s" % (pair, self.name)
+        mps_uri = ("mongodb://%s/?replicaSet=%s;maxPoolSize=10"
+                   % (pair, self.name))
+
+        client = MongoReplicaSetClient(uri)
+        self.assertEqual(client.max_pool_size, 100)
+
+        client = MongoReplicaSetClient(uri, maxPoolSize=10)
+        self.assertEqual(client.max_pool_size, 10)
+
+        client = MongoReplicaSetClient(uri, max_pool_size=8, maxPoolSize=10)
+        self.assertEqual(client.max_pool_size, 10)
+
+        client = MongoReplicaSetClient(mps_uri)
+        self.assertEqual(client.max_pool_size, 10)
+
+        client = MongoReplicaSetClient(mps_uri, max_pool_size=8)
+        self.assertEqual(client.max_pool_size, 10)
+
+        client = MongoReplicaSetClient(mps_uri, maxPoolSize=8)
+        self.assertEqual(client.max_pool_size, 10)
+
+        client = MongoReplicaSetClient(mps_uri, max_pool_size=6, maxPoolSize=8)
+        self.assertEqual(client.max_pool_size, 10)
+
     def test_backport_repl_localthresholdms_uri(self):
         uri = ("mongodb://%s/?replicaSet=%s" % (pair, self.name))
         lt_uri = ("mongodb://%s/?replicaSet=%s;localThresholdMS=10"
diff --git a/test/test_uri_parser.py b/test/test_uri_parser.py
index 499688e22..163ff1264 100644
--- a/test/test_uri_parser.py
+++ b/test/test_uri_parser.py
@@ -136,8 +136,7 @@ class TestURI(unittest.TestCase):
         self.assertRaises(ConfigurationError,
                           split_options, 'authMechanism=foo')
         self.assertEqual({'authsource': 'foobar'}, split_options('authSource=foobar'))
-        # maxPoolSize isn't yet a documented URI option.
-        self.assertRaises(ConfigurationError, split_options, 'maxpoolsize=50')
+        self.assertEqual({'maxpoolsize': 50}, split_options('maxpoolsize=50'))
         self.assertEqual({'localthresholdms': 300},
                          split_options('localThresholdMS=300'))