diff --git a/python/src/typechat/_internal/model.py b/python/src/typechat/_internal/model.py
index 471404f0..42e412a1 100644
--- a/python/src/typechat/_internal/model.py
+++ b/python/src/typechat/_internal/model.py
@@ -180,7 +180,7 @@ def required_var(name: str) -> str:
         api_key = required_var("OPENAI_API_KEY")
         model = required_var("OPENAI_MODEL")
         endpoint = vals.get("OPENAI_ENDPOINT", None) or "https://api.openai.com/v1/chat/completions"
-        org = vals.get("OPENAI_ORG", None) or ""
+        org = vals.get("OPENAI_ORGANIZATION", None) or vals.get("OPENAI_ORG", None) or ""
         return create_openai_language_model(api_key, model, endpoint, org)
 
     elif "AZURE_OPENAI_API_KEY" in vals:
diff --git a/python/tests/test_create_language_model.py b/python/tests/test_create_language_model.py
new file mode 100644
index 00000000..62dbe01c
--- /dev/null
+++ b/python/tests/test_create_language_model.py
@@ -0,0 +1,40 @@
+"""
+Tests for create_language_model's handling of the OpenAI organization variables.
+
+These only inspect the constructed model, so no request is sent.
+"""
+
+import typechat
+
+def test_openai_organization_is_sent_as_organization_header():
+    model = typechat.create_language_model(
+        {
+            "OPENAI_MODEL": "gpt-4o",
+            "OPENAI_API_KEY": "openai-secret",
+            "OPENAI_ORGANIZATION": "org-123",
+        }
+    )
+    assert model.headers["OpenAI-Organization"] == "org-123"
+
+
+def test_openai_org_is_still_sent_as_organization_header():
+    model = typechat.create_language_model(
+        {
+            "OPENAI_MODEL": "gpt-4o",
+            "OPENAI_API_KEY": "openai-secret",
+            "OPENAI_ORG": "org-legacy",
+        }
+    )
+    assert model.headers["OpenAI-Organization"] == "org-legacy"
+
+
+def test_openai_organization_takes_precedence_over_openai_org():
+    model = typechat.create_language_model(
+        {
+            "OPENAI_MODEL": "gpt-4o",
+            "OPENAI_API_KEY": "openai-secret",
+            "OPENAI_ORGANIZATION": "org-123",
+            "OPENAI_ORG": "org-legacy",
+        }
+    )
+    assert model.headers["OpenAI-Organization"] == "org-123"