diff --git a/setup.py b/setup.py
index 28aa5a5c8e8..5d33756c191 100644
--- a/setup.py
+++ b/setup.py
@@ -47,10 +47,10 @@ from setuptools.command import egg_info
 egg_info.manifest_maker.template = 'PYTHON-MANIFEST.in'
 
 PY3 = sys.version_info.major == 3
-PYTHON_STEM = './src/python/grpcio'
-CORE_INCLUDE = ('./include', '.',)
-BORINGSSL_INCLUDE = ('./third_party/boringssl/include',)
-ZLIB_INCLUDE = ('./third_party/zlib',)
+PYTHON_STEM = os.path.join('src', 'python', 'grpcio')
+CORE_INCLUDE = ('include', '.',)
+BORINGSSL_INCLUDE = (os.path.join('third_party', 'boringssl', 'include'),)
+ZLIB_INCLUDE = (os.path.join('third_party', 'zlib'),)
 
 # Ensure we're in the proper directory whether or not we're being used by pip.
 os.chdir(os.path.dirname(os.path.abspath(__file__)))
@@ -105,7 +105,9 @@ if not "win32" in sys.platform:
 if "win32" in sys.platform:
   EXTENSION_LIBRARIES += ('ws2_32',)
 
-DEFINE_MACROS = (('OPENSSL_NO_ASM', 1), ('_WIN32_WINNT', 0x600), ('GPR_BACKWARDS_COMPATIBILITY_MODE', 1),)
+DEFINE_MACROS = (
+    ('OPENSSL_NO_ASM', 1), ('_WIN32_WINNT', 0x600),
+    ('GPR_BACKWARDS_COMPATIBILITY_MODE', 1),)
 if "win32" in sys.platform:
   DEFINE_MACROS += (('OPENSSL_WINDOWS', 1), ('WIN32_LEAN_AND_MEAN', 1),)
   if '64bit' in platform.architecture()[0]:
@@ -200,12 +202,13 @@ COMMAND_CLASS = {
 }
 
 # Ensure that package data is copied over before any commands have been run:
-credentials_dir = os.path.join(PYTHON_STEM, 'grpc/_cython/_credentials')
+credentials_dir = os.path.join(PYTHON_STEM, 'grpc', '_cython', '_credentials')
 try:
   os.mkdir(credentials_dir)
 except OSError:
   pass
-shutil.copyfile('etc/roots.pem', os.path.join(credentials_dir, 'roots.pem'))
+shutil.copyfile(os.path.join('etc', 'roots.pem'),
+                os.path.join(credentials_dir, 'roots.pem'))
 
 PACKAGE_DATA = {
     # Binaries that may or may not be present in the final installation, but are
diff --git a/tools/distrib/python/grpcio_tools/setup.py b/tools/distrib/python/grpcio_tools/setup.py
index d804f34fc60..a00ce011107 100644
--- a/tools/distrib/python/grpcio_tools/setup.py
+++ b/tools/distrib/python/grpcio_tools/setup.py
@@ -61,6 +61,13 @@ EXTRA_COMPILE_ARGS = shlex.split(os.environ.get('GRPC_PYTHON_CFLAGS',
 EXTRA_LINK_ARGS = shlex.split(os.environ.get('GRPC_PYTHON_LDFLAGS',
                                              '-lpthread'))
 
+CC_FILES = [
+  os.path.normpath(cc_file) for cc_file in protoc_lib_deps.CC_FILES]
+PROTO_FILES = [
+  os.path.normpath(proto_file) for proto_file in protoc_lib_deps.PROTO_FILES]
+CC_INCLUDE = os.path.normpath(protoc_lib_deps.CC_INCLUDE)
+PROTO_INCLUDE = os.path.normpath(protoc_lib_deps.PROTO_INCLUDE)
+
 GRPC_PYTHON_TOOLS_PACKAGE = 'grpc.tools'
 GRPC_PYTHON_PROTO_RESOURCES_NAME = '_proto'
 
@@ -82,8 +89,8 @@ def package_data():
   proto_resources_path = os.path.join(tools_path,
                                       GRPC_PYTHON_PROTO_RESOURCES_NAME)
   proto_files = []
-  for proto_file in protoc_lib_deps.PROTO_FILES:
-    source = os.path.join(protoc_lib_deps.PROTO_INCLUDE, proto_file)
+  for proto_file in PROTO_FILES:
+    source = os.path.join(PROTO_INCLUDE, proto_file)
     target = os.path.join(proto_resources_path, proto_file)
     relative_target = os.path.join(GRPC_PYTHON_PROTO_RESOURCES_NAME, proto_file)
     try:
@@ -99,18 +106,20 @@ def package_data():
 
 def protoc_ext_module():
   plugin_sources = [
-      'grpc/tools/main.cc',
-      'grpc_root/src/compiler/python_generator.cc'] + [
-      os.path.join(protoc_lib_deps.CC_INCLUDE, cc_file)
-      for cc_file in protoc_lib_deps.CC_FILES]
+      os.path.join('grpc', 'tools', 'main.cc'),
+      os.path.join('grpc_root', 'src', 'compiler', 'python_generator.cc')] + [
+      os.path.join(CC_INCLUDE, cc_file)
+      for cc_file in CC_FILES]
   plugin_ext = extension.Extension(
       name='grpc.tools._protoc_compiler',
-      sources=['grpc/tools/_protoc_compiler.pyx'] + plugin_sources,
+      sources=(
+          [os.path.join('grpc', 'tools', '_protoc_compiler.pyx')] +
+          plugin_sources),
       include_dirs=[
           '.',
           'grpc_root',
-          'grpc_root/include',
-          protoc_lib_deps.CC_INCLUDE,
+          os.path.join('grpc_root', 'include'),
+          CC_INCLUDE,
       ],
       language='c++',
       define_macros=list(DEFINE_MACROS),