diff --git a/src/openai/_client.py b/src/openai/_client.py
index aadf3601f2..04261feace 100644
--- a/src/openai/_client.py
+++ b/src/openai/_client.py
@@ -161,7 +161,7 @@ def __init__(
         self.websocket_base_url = websocket_base_url
 
         if base_url is None:
-            base_url = os.environ.get("OPENAI_BASE_URL")
+            base_url = os.environ.get("OPENAI_BASE_URL") or None
         if base_url is None:
             base_url = f"https://api.openai.com/v1"
 
@@ -536,7 +536,7 @@ def __init__(
         self.websocket_base_url = websocket_base_url
 
         if base_url is None:
-            base_url = os.environ.get("OPENAI_BASE_URL")
+            base_url = os.environ.get("OPENAI_BASE_URL") or None
         if base_url is None:
             base_url = f"https://api.openai.com/v1"
 
diff --git a/tests/test_client.py b/tests/test_client.py
index a015cd7d40..995e9e1edc 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -696,6 +696,11 @@ def test_base_url_env(self) -> None:
             client = OpenAI(api_key=api_key, _strict_response_validation=True)
             assert client.base_url == "http://localhost:5000/from/env/"
 
+    def test_base_url_env_empty_string(self) -> None:
+        with update_env(OPENAI_BASE_URL=""):
+            client = OpenAI(api_key=api_key, _strict_response_validation=True)
+            assert client.base_url == "https://api.openai.com/v1/"
+
     @pytest.mark.parametrize(
         "client",
         [
@@ -1734,6 +1739,11 @@ async def test_base_url_env(self) -> None:
             client = AsyncOpenAI(api_key=api_key, _strict_response_validation=True)
             assert client.base_url == "http://localhost:5000/from/env/"
 
+    async def test_base_url_env_empty_string(self) -> None:
+        with update_env(OPENAI_BASE_URL=""):
+            client = AsyncOpenAI(api_key=api_key, _strict_response_validation=True)
+            assert client.base_url == "https://api.openai.com/v1/"
+
     @pytest.mark.parametrize(
         "client",
         [