diff --git a/HISTORY.rst b/HISTORY.rst
index 9319c2a4..b5fc4dc7 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -13,6 +13,7 @@ PlatformIO 4.0
 * Do not shutdown PIO Home Server for "upgrade" operations (`issue #2784 <https://github.com/platformio/platformio-core/issues/2784>`_)
 * Improved computing of project check sum (structure, configuration) and avoid unnecessary rebuilding
 * Improved printing of tabulated results
+* Automatically normalize file system paths to UNIX-style for Project Generator (`issue #2857 <https://github.com/platformio/platformio-core/issues/2857>`_)
 * Ability to set "databaseFilename" for VSCode and C/C++ extension (`issue #2825 <https://github.com/platformio/platformio-core/issues/2825>`_)
 * Renamed "enable_ssl" setting to `strict_ssl <http://docs.platformio.org/page/userguide/cmd_settings.html#strict-ssl>`__
 * Fixed an issue with incorrect escaping of Windows slashes when using `PIO Unified Debugger <http://docs.platformio.org/page/plus/debugging.html>`__ and "piped" openOCD
diff --git a/platformio/ide/projectgenerator.py b/platformio/ide/projectgenerator.py
index 99170482..afc54473 100644
--- a/platformio/ide/projectgenerator.py
+++ b/platformio/ide/projectgenerator.py
@@ -73,10 +73,10 @@ class ProjectGenerator(object):
             "project_dir": self.project_dir,
             "env_name": self.env_name,
             "user_home_dir": abspath(expanduser("~")),
-            "platformio_path": self._fix_os_path(
+            "platformio_path":
                 sys.argv[0] if isfile(sys.argv[0])
-                else where_is_program("platformio")),
-            "env_path": self._fix_os_path(os.getenv("PATH")),
+                else where_is_program("platformio"),
+            "env_path": os.getenv("PATH"),
             "env_pathsep": os.pathsep
         }   # yapf: disable
 
@@ -95,11 +95,23 @@ class ProjectGenerator(object):
                     get_project_libdeps_dir(), self.env_name)
 
             })  # yapf: disable
+
+        for key, value in tpl_vars.items():
+            if key.endswith(("_path", "_dir")):
+                tpl_vars[key] = self.to_unix_path(value)
+        for key in ("includes", "src_files", "libsource_dirs"):
+            if key not in tpl_vars:
+                continue
+            tpl_vars[key] = [self.to_unix_path(inc) for inc in tpl_vars[key]]
+
+        tpl_vars['to_unix_path'] = self.to_unix_path
         return tpl_vars
 
     @staticmethod
-    def _fix_os_path(path):
-        return (re.sub(r"[\\]+", '\\' * 4, path) if WINDOWS else path)
+    def to_unix_path(path):
+        if not WINDOWS or not path:
+            return path
+        return re.sub(r"[\\]+", "/", path)
 
     def get_src_files(self):
         result = []
diff --git a/platformio/ide/tpls/atom/.gcc-flags.json.tpl b/platformio/ide/tpls/atom/.gcc-flags.json.tpl
index 20942a7a..cbb47418 100644
--- a/platformio/ide/tpls/atom/.gcc-flags.json.tpl
+++ b/platformio/ide/tpls/atom/.gcc-flags.json.tpl
@@ -1,9 +1,9 @@
 % _defines = " ".join(["-D%s" % d for d in defines])
 {
-  "execPath": "{{ cxx_path.replace("\\", "/") }}",
+  "execPath": "{{ cxx_path }}",
   "gccDefaultCFlags": "-fsyntax-only {{! cc_flags.replace(' -MMD ', ' ').replace('"', '\\"') }} {{ !_defines.replace('"', '\\"') }}",
   "gccDefaultCppFlags": "-fsyntax-only {{! cxx_flags.replace(' -MMD ', ' ').replace('"', '\\"') }} {{ !_defines.replace('"', '\\"') }}",
   "gccErrorLimit": 15,
-  "gccIncludePaths": "{{ ','.join(includes).replace("\\", "/") }}",
+  "gccIncludePaths": "{{ ','.join(includes) }}",
   "gccSuppressWarnings": false
 }
diff --git a/platformio/ide/tpls/clion/CMakeListsPrivate.txt.tpl b/platformio/ide/tpls/clion/CMakeListsPrivate.txt.tpl
index b3d84a75..5d69c4d8 100644
--- a/platformio/ide/tpls/clion/CMakeListsPrivate.txt.tpl
+++ b/platformio/ide/tpls/clion/CMakeListsPrivate.txt.tpl
@@ -17,7 +17,7 @@
 %       path = path.replace(user_home_dir, "$ENV{HOME}")
 %     end
 %   end
-%   return path.replace("\\", "/")
+%   return path
 % end
 
 set(PLATFORMIO_CMD "{{ _normalize_path(platformio_path) }}")
diff --git a/platformio/ide/tpls/codeblocks/platformio.cbp.tpl b/platformio/ide/tpls/codeblocks/platformio.cbp.tpl
index fc182531..ccbe4d7f 100644
--- a/platformio/ide/tpls/codeblocks/platformio.cbp.tpl
+++ b/platformio/ide/tpls/codeblocks/platformio.cbp.tpl
@@ -53,12 +53,12 @@
 			<Add option="-D{{define}}"/>
 			% end
 			% for include in includes:
-			<Add directory="{{include.replace("\\", "/")}}"/>
-			% end		
+			<Add directory="{{include}}"/>
+			% end
 		</Compiler>
 		<Unit filename="platformio.ini" />
 		% for file in src_files:
-		<Unit filename="{{file.replace("\\", "/")}}"></Unit>
+		<Unit filename="{{file}}"></Unit>
 		% end
 	</Project>
 </CodeBlocks_project_file>
diff --git a/platformio/ide/tpls/vim/.gcc-flags.json.tpl b/platformio/ide/tpls/vim/.gcc-flags.json.tpl
index b904e1a3..b9b29fdb 100644
--- a/platformio/ide/tpls/vim/.gcc-flags.json.tpl
+++ b/platformio/ide/tpls/vim/.gcc-flags.json.tpl
@@ -1,9 +1,9 @@
 % _defines = " ".join(["-D%s" % d for d in defines])
 {
-  "execPath": "{{ cxx_path.replace("\\", "/") }}",
+  "execPath": "{{ cxx_path }}",
   "gccDefaultCFlags": "-fsyntax-only {{! cc_flags.replace(' -MMD ', ' ').replace('"', '\\"') }} {{ !_defines.replace('"', '\\"') }}",
   "gccDefaultCppFlags": "-fsyntax-only {{! cxx_flags.replace(' -MMD ', ' ').replace('"', '\\"') }} {{ !_defines.replace('"', '\\"') }}",
   "gccErrorLimit": 15,
-  "gccIncludePaths": "{{! ','.join("'{}'".format(w.replace("\\", '/')) for w in includes)}}",
+  "gccIncludePaths": "{{! ','.join("'{}'".format(inc) for inc in includes)}}",
   "gccSuppressWarnings": false
 }
diff --git a/platformio/ide/tpls/vscode/.vscode/c_cpp_properties.json.tpl b/platformio/ide/tpls/vscode/.vscode/c_cpp_properties.json.tpl
index 23fef0eb..7dd647fc 100644
--- a/platformio/ide/tpls/vscode/.vscode/c_cpp_properties.json.tpl
+++ b/platformio/ide/tpls/vscode/.vscode/c_cpp_properties.json.tpl
@@ -10,7 +10,7 @@
 % systype = platform.system().lower()
 %
 % def _escape(text):
-%   return text.replace('\\\\', '/').replace('\\', '/').replace('"', '\\"')
+%   return to_unix_path(text).replace('"', '\\"')
 % end
 %
 % cleaned_includes = []
@@ -30,7 +30,7 @@
 % end
             "includePath": [
 % for include in cleaned_includes:
-                "{{! _escape(include) }}",
+                "{{ include }}",
 % end
                 ""
             ],
@@ -38,7 +38,7 @@
                 "limitSymbolsToIncludedHeaders": true,
                 "path": [
 % for include in cleaned_includes:
-                    "{{! _escape(include) }}",
+                    "{{ include }}",
 % end
                     ""
                 ]
@@ -64,7 +64,7 @@
 % if cxx_stds:
             "cppStandard": "c++{{ cxx_stds[-1] }}",
 % end
-            "compilerPath": "\"{{! _escape(cc_path) }}\" {{! _escape(cc_m_flags) }}"
+            "compilerPath": "\"{{cc_path}}\" {{! _escape(cc_m_flags) }}"
         }
     ],
     "version": 4