diff --git a/src/mcp/server/fastmcp/server.py b/src/mcp/server/fastmcp/server.py
index bf0ce880a5..15bbea1fe0 100644
--- a/src/mcp/server/fastmcp/server.py
+++ b/src/mcp/server/fastmcp/server.py
@@ -75,6 +75,7 @@ class Settings(BaseSettings, Generic[LifespanResultT]):
     port: int = 8000
     sse_path: str = "/sse"
     message_path: str = "/messages/"
+    base_path: str = "/"
 
     # resource settings
     warn_on_duplicate_resources: bool = True
@@ -479,7 +480,7 @@ async def run_sse_async(self) -> None:
 
     def sse_app(self) -> Starlette:
         """Return an instance of the SSE server app."""
-        sse = SseServerTransport(self.settings.message_path)
+        sse = SseServerTransport(self.settings.message_path, self.settings.base_path)
 
         async def handle_sse(request: Request) -> None:
             async with sse.connect_sse(
diff --git a/src/mcp/server/sse.py b/src/mcp/server/sse.py
index d051c25bf6..bb0911cc40 100644
--- a/src/mcp/server/sse.py
+++ b/src/mcp/server/sse.py
@@ -36,6 +36,8 @@ async def handle_sse(request):
 from typing import Any
 from urllib.parse import quote
 from uuid import UUID, uuid4
+import os
+import re
 
 import anyio
 from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
@@ -67,7 +69,7 @@ class SseServerTransport:
         UUID, MemoryObjectSendStream[types.JSONRPCMessage | Exception]
     ]
 
-    def __init__(self, endpoint: str) -> None:
+    def __init__(self, endpoint: str, base_path: str) -> None:
         """
         Creates a new SSE server transport, which will direct the client to POST
         messages to the relative or absolute URL given.
@@ -75,6 +77,7 @@ def __init__(self, endpoint: str) -> None:
 
         super().__init__()
         self._endpoint = endpoint
+        self._base_path = base_path
         self._read_stream_writers = {}
         logger.debug(f"SseServerTransport initialized with endpoint: {endpoint}")
 
@@ -96,6 +99,8 @@ async def connect_sse(self, scope: Scope, receive: Receive, send: Send):
 
         session_id = uuid4()
         session_uri = f"{quote(self._endpoint)}?session_id={session_id.hex}"
+        # join the base path and endpoint
+        session_full_url = os.path.join(self._base_path, re.sub("^/", "", session_uri, 1))
         self._read_stream_writers[session_id] = read_stream_writer
         logger.debug(f"Created new session with ID: {session_id}")
 
@@ -106,8 +111,8 @@ async def connect_sse(self, scope: Scope, receive: Receive, send: Send):
         async def sse_writer():
             logger.debug("Starting SSE writer")
             async with sse_stream_writer, write_stream_reader:
-                await sse_stream_writer.send({"event": "endpoint", "data": session_uri})
-                logger.debug(f"Sent endpoint event: {session_uri}")
+                await sse_stream_writer.send({"event": "endpoint", "data": session_full_url})
+                logger.debug(f"Sent endpoint event: {session_full_url}")
 
                 async for message in write_stream_reader:
                     logger.debug(f"Sending message via SSE: {message}")