diff --git a/asyncpg/connection.py b/asyncpg/connection.py
index 77fbf48e..26e8ea37 100644
--- a/asyncpg/connection.py
+++ b/asyncpg/connection.py
@@ -13,6 +13,7 @@
 import struct
 import time
 import urllib.parse
+import warnings
 
 from . import cursor
 from . import exceptions
@@ -216,7 +217,12 @@ async def execute(self, query: str, *args, timeout: float=None) -> str:
         _, status, _ = await self._execute(query, args, 0, timeout, True)
         return status.decode()
 
-    async def executemany(self, command: str, args, timeout: float=None):
+    async def executemany(self, command: str, args,
+                          _timeout: float=None, **kw):
+        # The real signature of this method is:
+        #
+        #     executemany(self, command: str, args, *, timeout: float=None)
+        #
         """Execute an SQL *command* for each sequence of arguments in *args*.
 
         Example:
@@ -234,6 +240,23 @@ async def executemany(self, command: str, args, timeout: float=None):
 
         .. versionadded:: 0.7.0
         """
+        if 'timeout' in kw:
+            timeout = kw.pop('timeout')
+        else:
+            timeout = _timeout
+            if timeout is not None:
+                warnings.warn(
+                    "Passing 'timeout' as a positional argument to "
+                    "executemany() is deprecated and will be removed in "
+                    "asyncpg 0.11.0.  Pass it as a keyword argument instead: "
+                    "`executemany(..., timeout=...)`.",
+                    DeprecationWarning, stacklevel=2)
+        if kw:
+            first_kwarg = next(iter(kw))
+            raise TypeError(
+                'executemany() got an unexpected keyword argument {!r}'.format(
+                    first_kwarg))
+
         return await self._executemany(command, args, timeout)
 
     async def _get_statement(self, query, timeout, *, named: bool=False):
@@ -948,3 +971,21 @@ def _detect_server_capabilities(server_version, connection_settings):
         sql_reset=sql_reset,
         sql_close_all=sql_close_all
     )
+
+
+def _patch_executemany_signature():
+    # Patch Connection.executemany() signature to remove '**kw' parameter
+    # and change '_timeout' keyword arg to 'timeout' keyword-only arg.
+    # TODO Remove in 0.11.0.
+    import inspect
+    sig = inspect.signature(Connection.executemany)
+    params = sig.parameters.copy()
+    params.pop('kw')
+    timeout = params.pop('_timeout')
+    timeout = timeout.replace(name='timeout', kind=timeout.KEYWORD_ONLY)
+    params['timeout'] = timeout
+    Connection.executemany.__signature__ = sig.replace(
+        parameters=params.values())
+
+
+_patch_executemany_signature()
diff --git a/tests/test_execute.py b/tests/test_execute.py
index 31b667c4..249be033 100644
--- a/tests/test_execute.py
+++ b/tests/test_execute.py
@@ -7,6 +7,8 @@
 
 import asyncio
 import asyncpg
+import inspect
+import warnings
 
 from asyncpg import _testbase as tb
 
@@ -152,3 +154,29 @@ async def test_execute_many_2(self):
                 ''', good_data)
         finally:
             await self.con.execute('DROP TABLE exmany')
+
+    async def test_execute_many_3_kwonly_timeout(self):
+        with self.assertWarnsRegex(DeprecationWarning,
+                                   "Passing 'timeout' as a positional"):
+            await self.con.executemany(
+                '''SELECT $1::int''',
+                [(1,), (2,)],
+                1)
+
+        with warnings.catch_warnings():
+            warnings.simplefilter("error")
+
+            # Test that passing timeout as a kwarg doesn't trigger a warning.
+            await self.con.executemany(
+                '''SELECT $1::int''',
+                [(1,), (2,)],
+                timeout=1)
+
+            # Test that not passing timeout is fine too.
+            await self.con.executemany(
+                '''SELECT $1::int''',
+                [(1,), (2,)])
+
+        self.assertEqual(
+            str(inspect.signature(self.con.executemany)),
+            '(command:str, args, *, timeout:float=None)')