diff --git a/lib/chat_models/chat_open_ai.ex b/lib/chat_models/chat_open_ai.ex
index 1dea30e0..5a66d22c 100644
--- a/lib/chat_models/chat_open_ai.ex
+++ b/lib/chat_models/chat_open_ai.ex
@@ -246,7 +246,7 @@ defmodule LangChain.ChatModels.ChatOpenAI do
       Req.new(
         url: openai.endpoint,
         json: for_api(openai, messages, functions),
-        auth: {:bearer, get_api_key()},
+        auth: {:bearer, openai.api_key || get_api_key()},
         receive_timeout: openai.receive_timeout,
         retry: :transient,
         max_retries: 3,