diff --git a/modules/openapi-generator/src/main/resources/python-fastapi/api.mustache b/modules/openapi-generator/src/main/resources/python-fastapi/api.mustache
index 400685f0abcb..43d115853833 100644
--- a/modules/openapi-generator/src/main/resources/python-fastapi/api.mustache
+++ b/modules/openapi-generator/src/main/resources/python-fastapi/api.mustache
@@ -65,7 +65,7 @@ async def {{operationId}}(
     {{/hasAuthMethods}}
 ) -> {{returnType}}{{^returnType}}None{{/returnType}}:
     {{#notes}}"""{{.}}"""
-    return Base{{classname}}.subclasses[0]().{{operationId}}({{#allParams}}{{>impl_argument}}{{^-last}}, {{/-last}}{{/allParams}}){{/notes}}{{^notes}}...{{/notes}}
+    {{/notes}}return await Base{{classname}}.subclasses[0]().{{operationId}}({{#allParams}}{{>impl_argument}}{{^-last}}, {{/-last}}{{/allParams}})
 {{^-last}}
 
 
diff --git a/modules/openapi-generator/src/main/resources/python-fastapi/base_api.mustache b/modules/openapi-generator/src/main/resources/python-fastapi/base_api.mustache
index 2e80168a328c..d1d95c12eff8 100644
--- a/modules/openapi-generator/src/main/resources/python-fastapi/base_api.mustache
+++ b/modules/openapi-generator/src/main/resources/python-fastapi/base_api.mustache
@@ -15,7 +15,7 @@ class Base{{classname}}:
         Base{{classname}}.subclasses = Base{{classname}}.subclasses + (cls,)
 {{#operations}}
 {{#operation}}
-    def {{operationId}}(
+    async def {{operationId}}(
         self,
         {{#allParams}}
         {{>impl_argument_definition}},
diff --git a/samples/server/petstore/python-fastapi/src/openapi_server/apis/fake_api.py b/samples/server/petstore/python-fastapi/src/openapi_server/apis/fake_api.py
index eb90fbbfbb02..66a8d7fb4d3e 100644
--- a/samples/server/petstore/python-fastapi/src/openapi_server/apis/fake_api.py
+++ b/samples/server/petstore/python-fastapi/src/openapi_server/apis/fake_api.py
@@ -46,4 +46,4 @@ async def fake_query_param_default(
     no_default: str = Query(None, description="no default value", alias="noDefault"),
 ) -> None:
     """"""
-    return BaseFakeApi.subclasses[0]().fake_query_param_default(has_default, no_default)
+    return await BaseFakeApi.subclasses[0]().fake_query_param_default(has_default, no_default)
diff --git a/samples/server/petstore/python-fastapi/src/openapi_server/apis/fake_api_base.py b/samples/server/petstore/python-fastapi/src/openapi_server/apis/fake_api_base.py
index 6191845177f9..5af08fcbd8e9 100644
--- a/samples/server/petstore/python-fastapi/src/openapi_server/apis/fake_api_base.py
+++ b/samples/server/petstore/python-fastapi/src/openapi_server/apis/fake_api_base.py
@@ -10,7 +10,7 @@ class BaseFakeApi:
     def __init_subclass__(cls, **kwargs):
         super().__init_subclass__(**kwargs)
         BaseFakeApi.subclasses = BaseFakeApi.subclasses + (cls,)
-    def fake_query_param_default(
+    async def fake_query_param_default(
         self,
         has_default: str,
         no_default: str,
diff --git a/samples/server/petstore/python-fastapi/src/openapi_server/apis/pet_api.py b/samples/server/petstore/python-fastapi/src/openapi_server/apis/pet_api.py
index 1229ceeed197..56535370873c 100644
--- a/samples/server/petstore/python-fastapi/src/openapi_server/apis/pet_api.py
+++ b/samples/server/petstore/python-fastapi/src/openapi_server/apis/pet_api.py
@@ -50,7 +50,7 @@ async def add_pet(
     ),
 ) -> Pet:
     """"""
-    return BasePetApi.subclasses[0]().add_pet(pet)
+    return await BasePetApi.subclasses[0]().add_pet(pet)
 
 
 @router.delete(
@@ -70,7 +70,7 @@ async def delete_pet(
     ),
 ) -> None:
     """"""
-    return BasePetApi.subclasses[0]().delete_pet(petId, api_key)
+    return await BasePetApi.subclasses[0]().delete_pet(petId, api_key)
 
 
 @router.get(
@@ -90,7 +90,7 @@ async def find_pets_by_status(
     ),
 ) -> List[Pet]:
     """Multiple status values can be provided with comma separated strings"""
-    return BasePetApi.subclasses[0]().find_pets_by_status(status)
+    return await BasePetApi.subclasses[0]().find_pets_by_status(status)
 
 
 @router.get(
@@ -110,7 +110,7 @@ async def find_pets_by_tags(
     ),
 ) -> List[Pet]:
     """Multiple tags can be provided with comma separated strings. Use tag1, tag2, tag3 for testing."""
-    return BasePetApi.subclasses[0]().find_pets_by_tags(tags)
+    return await BasePetApi.subclasses[0]().find_pets_by_tags(tags)
 
 
 @router.get(
@@ -131,7 +131,7 @@ async def get_pet_by_id(
     ),
 ) -> Pet:
     """Returns a single pet"""
-    return BasePetApi.subclasses[0]().get_pet_by_id(petId)
+    return await BasePetApi.subclasses[0]().get_pet_by_id(petId)
 
 
 @router.put(
@@ -153,7 +153,7 @@ async def update_pet(
     ),
 ) -> Pet:
     """"""
-    return BasePetApi.subclasses[0]().update_pet(pet)
+    return await BasePetApi.subclasses[0]().update_pet(pet)
 
 
 @router.post(
@@ -174,7 +174,7 @@ async def update_pet_with_form(
     ),
 ) -> None:
     """"""
-    return BasePetApi.subclasses[0]().update_pet_with_form(petId, name, status)
+    return await BasePetApi.subclasses[0]().update_pet_with_form(petId, name, status)
 
 
 @router.post(
@@ -195,4 +195,4 @@ async def upload_file(
     ),
 ) -> ApiResponse:
     """"""
-    return BasePetApi.subclasses[0]().upload_file(petId, additional_metadata, file)
+    return await BasePetApi.subclasses[0]().upload_file(petId, additional_metadata, file)
diff --git a/samples/server/petstore/python-fastapi/src/openapi_server/apis/pet_api_base.py b/samples/server/petstore/python-fastapi/src/openapi_server/apis/pet_api_base.py
index e8dfbc4f5c79..db77ff6c6a36 100644
--- a/samples/server/petstore/python-fastapi/src/openapi_server/apis/pet_api_base.py
+++ b/samples/server/petstore/python-fastapi/src/openapi_server/apis/pet_api_base.py
@@ -12,7 +12,7 @@ class BasePetApi:
     def __init_subclass__(cls, **kwargs):
         super().__init_subclass__(**kwargs)
         BasePetApi.subclasses = BasePetApi.subclasses + (cls,)
-    def add_pet(
+    async def add_pet(
         self,
         pet: Pet,
     ) -> Pet:
@@ -20,7 +20,7 @@ def add_pet(
         ...
 
 
-    def delete_pet(
+    async def delete_pet(
         self,
         petId: int,
         api_key: str,
@@ -29,7 +29,7 @@ def delete_pet(
         ...
 
 
-    def find_pets_by_status(
+    async def find_pets_by_status(
         self,
         status: List[str],
     ) -> List[Pet]:
@@ -37,7 +37,7 @@ def find_pets_by_status(
         ...
 
 
-    def find_pets_by_tags(
+    async def find_pets_by_tags(
         self,
         tags: List[str],
     ) -> List[Pet]:
@@ -45,7 +45,7 @@ def find_pets_by_tags(
         ...
 
 
-    def get_pet_by_id(
+    async def get_pet_by_id(
         self,
         petId: int,
     ) -> Pet:
@@ -53,7 +53,7 @@ def get_pet_by_id(
         ...
 
 
-    def update_pet(
+    async def update_pet(
         self,
         pet: Pet,
     ) -> Pet:
@@ -61,7 +61,7 @@ def update_pet(
         ...
 
 
-    def update_pet_with_form(
+    async def update_pet_with_form(
         self,
         petId: int,
         name: str,
@@ -71,7 +71,7 @@ def update_pet_with_form(
         ...
 
 
-    def upload_file(
+    async def upload_file(
         self,
         petId: int,
         additional_metadata: str,
diff --git a/samples/server/petstore/python-fastapi/src/openapi_server/apis/store_api.py b/samples/server/petstore/python-fastapi/src/openapi_server/apis/store_api.py
index b583c10a625b..d367a22e62ea 100644
--- a/samples/server/petstore/python-fastapi/src/openapi_server/apis/store_api.py
+++ b/samples/server/petstore/python-fastapi/src/openapi_server/apis/store_api.py
@@ -46,7 +46,7 @@ async def delete_order(
     orderId: str = Path(..., description="ID of the order that needs to be deleted"),
 ) -> None:
     """For valid response try integer IDs with value < 1000. Anything above 1000 or nonintegers will generate API errors"""
-    return BaseStoreApi.subclasses[0]().delete_order(orderId)
+    return await BaseStoreApi.subclasses[0]().delete_order(orderId)
 
 
 @router.get(
@@ -64,7 +64,7 @@ async def get_inventory(
     ),
 ) -> Dict[str, int]:
     """Returns a map of status codes to quantities"""
-    return BaseStoreApi.subclasses[0]().get_inventory()
+    return await BaseStoreApi.subclasses[0]().get_inventory()
 
 
 @router.get(
@@ -82,7 +82,7 @@ async def get_order_by_id(
     orderId: int = Path(..., description="ID of pet that needs to be fetched", ge=1, le=5),
 ) -> Order:
     """For valid response try integer IDs with value <= 5 or > 10. Other values will generate exceptions"""
-    return BaseStoreApi.subclasses[0]().get_order_by_id(orderId)
+    return await BaseStoreApi.subclasses[0]().get_order_by_id(orderId)
 
 
 @router.post(
@@ -99,4 +99,4 @@ async def place_order(
     order: Order = Body(None, description="order placed for purchasing the pet"),
 ) -> Order:
     """"""
-    return BaseStoreApi.subclasses[0]().place_order(order)
+    return await BaseStoreApi.subclasses[0]().place_order(order)
diff --git a/samples/server/petstore/python-fastapi/src/openapi_server/apis/store_api_base.py b/samples/server/petstore/python-fastapi/src/openapi_server/apis/store_api_base.py
index f4436a6f07ea..40c01de8b941 100644
--- a/samples/server/petstore/python-fastapi/src/openapi_server/apis/store_api_base.py
+++ b/samples/server/petstore/python-fastapi/src/openapi_server/apis/store_api_base.py
@@ -11,7 +11,7 @@ class BaseStoreApi:
     def __init_subclass__(cls, **kwargs):
         super().__init_subclass__(**kwargs)
         BaseStoreApi.subclasses = BaseStoreApi.subclasses + (cls,)
-    def delete_order(
+    async def delete_order(
         self,
         orderId: str,
     ) -> None:
@@ -19,14 +19,14 @@ def delete_order(
         ...
 
 
-    def get_inventory(
+    async def get_inventory(
         self,
     ) -> Dict[str, int]:
         """Returns a map of status codes to quantities"""
         ...
 
 
-    def get_order_by_id(
+    async def get_order_by_id(
         self,
         orderId: int,
     ) -> Order:
@@ -34,7 +34,7 @@ def get_order_by_id(
         ...
 
 
-    def place_order(
+    async def place_order(
         self,
         order: Order,
     ) -> Order:
diff --git a/samples/server/petstore/python-fastapi/src/openapi_server/apis/user_api.py b/samples/server/petstore/python-fastapi/src/openapi_server/apis/user_api.py
index 1ee291c2a02b..5bbd3240d8db 100644
--- a/samples/server/petstore/python-fastapi/src/openapi_server/apis/user_api.py
+++ b/samples/server/petstore/python-fastapi/src/openapi_server/apis/user_api.py
@@ -48,7 +48,7 @@ async def create_user(
     ),
 ) -> None:
     """This can only be done by the logged in user."""
-    return BaseUserApi.subclasses[0]().create_user(user)
+    return await BaseUserApi.subclasses[0]().create_user(user)
 
 
 @router.post(
@@ -67,7 +67,7 @@ async def create_users_with_array_input(
     ),
 ) -> None:
     """"""
-    return BaseUserApi.subclasses[0]().create_users_with_array_input(user)
+    return await BaseUserApi.subclasses[0]().create_users_with_array_input(user)
 
 
 @router.post(
@@ -86,7 +86,7 @@ async def create_users_with_list_input(
     ),
 ) -> None:
     """"""
-    return BaseUserApi.subclasses[0]().create_users_with_list_input(user)
+    return await BaseUserApi.subclasses[0]().create_users_with_list_input(user)
 
 
 @router.delete(
@@ -106,7 +106,7 @@ async def delete_user(
     ),
 ) -> None:
     """This can only be done by the logged in user."""
-    return BaseUserApi.subclasses[0]().delete_user(username)
+    return await BaseUserApi.subclasses[0]().delete_user(username)
 
 
 @router.get(
@@ -124,7 +124,7 @@ async def get_user_by_name(
     username: str = Path(..., description="The name that needs to be fetched. Use user1 for testing."),
 ) -> User:
     """"""
-    return BaseUserApi.subclasses[0]().get_user_by_name(username)
+    return await BaseUserApi.subclasses[0]().get_user_by_name(username)
 
 
 @router.get(
@@ -142,7 +142,7 @@ async def login_user(
     password: str = Query(None, description="The password for login in clear text", alias="password"),
 ) -> str:
     """"""
-    return BaseUserApi.subclasses[0]().login_user(username, password)
+    return await BaseUserApi.subclasses[0]().login_user(username, password)
 
 
 @router.get(
@@ -160,7 +160,7 @@ async def logout_user(
     ),
 ) -> None:
     """"""
-    return BaseUserApi.subclasses[0]().logout_user()
+    return await BaseUserApi.subclasses[0]().logout_user()
 
 
 @router.put(
@@ -181,4 +181,4 @@ async def update_user(
     ),
 ) -> None:
     """This can only be done by the logged in user."""
-    return BaseUserApi.subclasses[0]().update_user(username, user)
+    return await BaseUserApi.subclasses[0]().update_user(username, user)
diff --git a/samples/server/petstore/python-fastapi/src/openapi_server/apis/user_api_base.py b/samples/server/petstore/python-fastapi/src/openapi_server/apis/user_api_base.py
index ee3314e7fa6b..b260864f1ca6 100644
--- a/samples/server/petstore/python-fastapi/src/openapi_server/apis/user_api_base.py
+++ b/samples/server/petstore/python-fastapi/src/openapi_server/apis/user_api_base.py
@@ -11,7 +11,7 @@ class BaseUserApi:
     def __init_subclass__(cls, **kwargs):
         super().__init_subclass__(**kwargs)
         BaseUserApi.subclasses = BaseUserApi.subclasses + (cls,)
-    def create_user(
+    async def create_user(
         self,
         user: User,
     ) -> None:
@@ -19,7 +19,7 @@ def create_user(
         ...
 
 
-    def create_users_with_array_input(
+    async def create_users_with_array_input(
         self,
         user: List[User],
     ) -> None:
@@ -27,7 +27,7 @@ def create_users_with_array_input(
         ...
 
 
-    def create_users_with_list_input(
+    async def create_users_with_list_input(
         self,
         user: List[User],
     ) -> None:
@@ -35,7 +35,7 @@ def create_users_with_list_input(
         ...
 
 
-    def delete_user(
+    async def delete_user(
         self,
         username: str,
     ) -> None:
@@ -43,7 +43,7 @@ def delete_user(
         ...
 
 
-    def get_user_by_name(
+    async def get_user_by_name(
         self,
         username: str,
     ) -> User:
@@ -51,7 +51,7 @@ def get_user_by_name(
         ...
 
 
-    def login_user(
+    async def login_user(
         self,
         username: str,
         password: str,
@@ -60,14 +60,14 @@ def login_user(
         ...
 
 
-    def logout_user(
+    async def logout_user(
         self,
     ) -> None:
         """"""
         ...
 
 
-    def update_user(
+    async def update_user(
         self,
         username: str,
         user: User,