diff --git a/fast_cache_middleware/controller.py b/fast_cache_middleware/controller.py
index 1078c1d..27a23f6 100644
--- a/fast_cache_middleware/controller.py
+++ b/fast_cache_middleware/controller.py
@@ -4,8 +4,10 @@
 from hashlib import blake2b
 from typing import Optional
 
+from starlette.concurrency import run_in_threadpool
 from starlette.requests import Request
 from starlette.responses import Response
+from starlette.routing import is_async_callable
 
 from .exceptions import NotFoundStorageError, TTLExpiredStorageError
 from .schemas import CacheConfiguration
@@ -140,20 +142,13 @@ async def is_cachable_response(self, response: Response) -> bool:
     async def generate_cache_key(
         self, request: Request, cache_configuration: CacheConfiguration
     ) -> str:
-        """Generates cache key for request.
-
-        Args:
-            request: HTTP request
-            cache_config: Cache configuration
-
-        Returns:
-            str: Cache key
-        """
-        # Use custom key generation function if available
         if cache_configuration.key_func:
-            return cache_configuration.key_func(request)
+            kf = cache_configuration.key_func
+
+            if is_async_callable(kf):
+                return await kf(request)  # type: ignore[no-any-return]
+            return await run_in_threadpool(kf, request)  # type: ignore[arg-type]
 
-        # Use standard function
         return generate_key(request)
 
     async def cache_response(
diff --git a/fast_cache_middleware/depends.py b/fast_cache_middleware/depends.py
index 88756f4..a4b8a81 100644
--- a/fast_cache_middleware/depends.py
+++ b/fast_cache_middleware/depends.py
@@ -1,9 +1,11 @@
 import re
-from typing import Callable, Optional
+from typing import Awaitable, Callable, Optional, Union
 
 from fastapi import params
 from starlette.requests import Request
 
+SyncOrAsync = Union[Callable[[Request], str], Callable[[Request], Awaitable[str]]]
+
 
 class BaseCacheConfigDepends(params.Depends):
     """Base class for cache configuration via ASGI scope extensions.
@@ -29,7 +31,7 @@ class CacheConfig(BaseCacheConfigDepends):
     def __init__(
         self,
         max_age: int = 5 * 60,
-        key_func: Optional[Callable[[Request], str]] = None,
+        key_func: Optional[SyncOrAsync] = None,
     ) -> None:
         self.max_age = max_age
         self.key_func = key_func
diff --git a/fast_cache_middleware/schemas.py b/fast_cache_middleware/schemas.py
index d4d9e4a..abe80b1 100644
--- a/fast_cache_middleware/schemas.py
+++ b/fast_cache_middleware/schemas.py
@@ -1,5 +1,5 @@
 import re
-from typing import Any, Callable
+from typing import Any
 
 from pydantic import (
     BaseModel,
@@ -9,10 +9,9 @@
     field_validator,
     model_validator,
 )
-from starlette.requests import Request
 from starlette.routing import Route
 
-from .depends import CacheConfig, CacheDropConfig
+from .depends import SyncOrAsync
 
 
 class CacheConfiguration(BaseModel):
@@ -22,7 +21,7 @@ class CacheConfiguration(BaseModel):
         default=None,
         description="Cache lifetime in seconds. If None, caching is disabled.",
     )
-    key_func: Callable[[Request], str] | None = Field(
+    key_func: SyncOrAsync | None = Field(
         default=None,
         description="Custom cache key generation function. If None, default key generation is used.",
     )