diff --git a/pyfactorybridge/__init__.py b/pyfactorybridge/__init__.py
index b653d4d..7fcc594 100644
--- a/pyfactorybridge/__init__.py
+++ b/pyfactorybridge/__init__.py
@@ -1,5 +1,7 @@
 import requests
 import logging
+from json import dumps
+from pathlib import Path
 
 from pyfactorybridge.exceptions import ServerExceptions, ServerError
 from pyfactorybridge.authentication import BearerAuth
@@ -34,19 +36,47 @@ def __init__(self, address, password=None, token=None):
         else:
             logging.error("No password provided, some functions may not work.")
 
-    def __request(self, function, properties={}) -> dict[Any]:
+    def __build_request_data(
+        self, function: str, properties: dict | None = None
+    ) -> dict:
         request_data = {"data": {"clientCustomData": ""}, "function": function}
-
-        for property_name, property_value in properties.items():
-            request_data["data"][property_name] = property_value
+        if isinstance(properties, dict):
+            for property_name, property_value in properties.items():
+                request_data["data"][property_name] = property_value
+        return request_data
+
+    def __request(
+        self,
+        function: str,
+        properties: dict | None = None,
+        multiparts: dict | None = None,
+    ) -> dict[Any]:
+        request_data = self.__build_request_data(function, properties)
+
+        http_method_kwargs = {}
+        if multiparts is None:
+            # Simple application/json request
+            http_method_kwargs = {
+                "json": request_data,
+            }
+        else:
+            # multipart/form-data request
+            if "data" not in multiparts:
+                multiparts["data"] = (
+                    # Multipart file name
+                    None,
+                    # Multipart content (byte-like)
+                    dumps(request_data),
+                    # Content-Type
+                    "application/json",
+                )
+            http_method_kwargs = {
+                "files": multiparts,
+            }
 
         try:
             response_data = requests.post(
-                self.URL,
-                verify=False,
-                json=request_data,
-                auth=self.auth if self.auth else None,
-                headers={"Content-Type": "application/json"},
+                self.URL, verify=False, auth=self.auth, **http_method_kwargs
             )
 
             if response_data.text:
@@ -167,8 +197,35 @@ def load_game(self, SaveName, EnableAdvancedGameSettings) -> dict[str, str]:
             },
         )
 
-    def upload_save_game(self, data) -> None:
-        raise NotImplementedError
+    def upload_save_game(
+        self,
+        save_file_path: str,
+        SaveName: str | None = None,
+        LoadSaveGame: bool = False,
+        EnableAdvancedGameSettings: bool = False,
+    ) -> dict[str, str]:
+        with open(save_file_path, "rb") as save_file_handle:
+            save_file_path_obj = Path(save_file_path)
+            multiparts = {
+                "saveGameFile": (
+                    # Save file basename (including .sav)
+                    save_file_path_obj.name,
+                    # Save file content
+                    save_file_handle.read(),
+                    # Content-Type
+                    "application/octet-stream",
+                )
+            }
+            return self.__request(
+                function="UploadSaveGame",
+                properties={
+                    "SaveName": SaveName
+                    or save_file_path_obj.stem,  # Save file name without file extension
+                    "LoadSaveGame": LoadSaveGame,
+                    "EnableAdvancedGameSettings": EnableAdvancedGameSettings,
+                },
+                multiparts=multiparts,
+            )
 
     def download_save_game(self, SaveName) -> None:
         raise NotImplementedError