diff --git a/python/python/lancedb/rerankers/openai.py b/python/python/lancedb/rerankers/openai.py
index 49b067f79..75efbbfc7 100644
--- a/python/python/lancedb/rerankers/openai.py
+++ b/python/python/lancedb/rerankers/openai.py
@@ -131,4 +131,4 @@ class OpenaiReranker(Reranker):
                 "OPENAI_API_KEY not set. Either set it in your environment or \
                 pass it as `api_key` argument to the CohereReranker."
             )
-        return openai.OpenAI(api_key=os.environ.get("OPENAI_API_KEY") or self.api_key)
+        return openai.OpenAI(api_key=self.api_key or os.environ.get("OPENAI_API_KEY"))
diff --git a/python/python/tests/test_openai_reranker_credentials.py b/python/python/tests/test_openai_reranker_credentials.py
new file mode 100644
index 000000000..aa11239b2
--- /dev/null
+++ b/python/python/tests/test_openai_reranker_credentials.py
@@ -0,0 +1,38 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright The LanceDB Authors
+
+import pytest
+
+from lancedb.rerankers import OpenaiReranker
+
+
+@pytest.mark.parametrize(
+    "explicit_key, environment_key, expected_key",
+    [
+        ("explicit-test-key", "environment-test-key", "explicit-test-key"),
+        ("explicit-test-key", None, "explicit-test-key"),
+        (None, "environment-test-key", "environment-test-key"),
+    ],
+)
+def test_openai_reranker_api_key_precedence(
+    monkeypatch, explicit_key, environment_key, expected_key
+):
+    pytest.importorskip("openai")
+    if environment_key is None:
+        monkeypatch.delenv("OPENAI_API_KEY", raising=False)
+    else:
+        monkeypatch.setenv("OPENAI_API_KEY", environment_key)
+
+    reranker = OpenaiReranker(api_key=explicit_key)
+    client = reranker._client
+    try:
+        assert client.api_key == expected_key
+    finally:
+        client.close()
+
+
+def test_openai_reranker_requires_api_key(monkeypatch):
+    pytest.importorskip("openai")
+    monkeypatch.delenv("OPENAI_API_KEY", raising=False)
+    with pytest.raises(ValueError, match="OPENAI_API_KEY not set"):
+        OpenaiReranker()._client