diff --git a/pre_commit/languages/python.py b/pre_commit/languages/python.py
index 1e60a3ed..bc6c5a1f 100644
--- a/pre_commit/languages/python.py
+++ b/pre_commit/languages/python.py
@@ -73,10 +73,28 @@ def install_environment(
         else:
             venv_cmd.extend(['-p', os.path.realpath(sys.executable)])
         repo_cmd_runner.run(venv_cmd, cwd='/')
+
+        # Determine if items in additional_dependencies are pip requirements
+        # files or package names
+        packages = []
+        requirements_files = []
+        for dependency in additional_dependencies:
+            if dependency.startswith('file:'):
+                requirements_files.append(dependency.split('file:', 1)[1])
+            else:
+                packages.append(dependency)
+
         with in_env(repo_cmd_runner, version):
+            if requirements_files:
+                helpers.run_setup_cmd(
+                    repo_cmd_runner,
+                    ('pip', 'install') +
+                    tuple('-r{}'.format(req_file)
+                          for req_file in requirements_files),
+                )
             helpers.run_setup_cmd(
                 repo_cmd_runner,
-                ('pip', 'install', '.') + additional_dependencies,
+                ('pip', 'install', '.') + tuple(packages),
             )
 
 
diff --git a/tests/repository_test.py b/tests/repository_test.py
index f91642ee..bdd8bfa9 100644
--- a/tests/repository_test.py
+++ b/tests/repository_test.py
@@ -480,6 +480,30 @@ def test_additional_python_dependencies_installed(tempdir_factory, store):
         assert 'mccabe' in output
 
 
+@pytest.mark.integration
+def test_additional_python_dependencies_requirements_files(
+        tempdir_factory,
+        store
+):
+    path = make_repo(tempdir_factory, 'python_hooks_repo')
+    config = make_config_from_repo(path)
+
+    # write pip requirements file
+    req_file_path = os.path.join(path, 'requirements.txt')
+    with io.open(req_file_path, 'w') as fp:
+        fp.write('pep8')
+
+    config['hooks'][0]['additional_dependencies'] = \
+        ['mccabe', 'file:{}'.format(req_file_path)]
+
+    repo = Repository.create(config, store)
+    repo.require_installed()
+    with python.in_env(repo._cmd_runner, 'default'):
+        output = cmd_output('pip', 'freeze', '-l')[1]
+        assert 'mccabe' in output
+        assert 'pep8' in output
+
+
 @pytest.mark.integration
 def test_additional_dependencies_roll_forward(tempdir_factory, store):
     path = make_repo(tempdir_factory, 'python_hooks_repo')