diff --git a/aiogram/bot/bot.py b/aiogram/bot/bot.py
index 11409fcc..4ea34f8d 100644
--- a/aiogram/bot/bot.py
+++ b/aiogram/bot/bot.py
@@ -1147,20 +1147,32 @@ class Bot(BaseBot, DataMixin, ContextInstanceMixin):
         result = await self.request(api.Methods.KICK_CHAT_MEMBER, payload)
         return result
 
-    async def unban_chat_member(self, chat_id: typing.Union[base.Integer, base.String],
-                                user_id: base.Integer) -> base.Boolean:
+    async def unban_chat_member(self,
+                                chat_id: typing.Union[base.Integer, base.String],
+                                user_id: base.Integer,
+                                only_if_banned: typing.Optional[base.Boolean] = None,
+                                ) -> base.Boolean:
         """
-        Use this method to unban a previously kicked user in a supergroup or channel. `
-        The user will not return to the group or channel automatically, but will be able to join via link, etc.
-
-        The bot must be an administrator for this to work.
+        Use this method to unban a previously kicked user in a supergroup or channel.
+        The user will not return to the group or channel automatically, but will be
+        able to join via link, etc. The bot must be an administrator for this to
+        work. By default, this method guarantees that after the call the user is not
+        a member of the chat, but will be able to join it. So if the user is a member
+        of the chat they will also be removed from the chat. If you don't want this,
+        use the parameter only_if_banned. Returns True on success.
 
         Source: https://core.telegram.org/bots/api#unbanchatmember
 
-        :param chat_id: Unique identifier for the target group or username of the target supergroup or channel
+        :param chat_id: Unique identifier for the target group or username of the
+            target supergroup or channel (in the format @username)
         :type chat_id: :obj:`typing.Union[base.Integer, base.String]`
+
         :param user_id: Unique identifier of the target user
         :type user_id: :obj:`base.Integer`
+
+        :param only_if_banned: Do nothing if the user is not banned
+        :type only_if_banned: :obj:`typing.Optional[base.Boolean]`
+
         :return: Returns True on success
         :rtype: :obj:`base.Boolean`
         """