diff --git a/src/agents/tracing/processors.py b/src/agents/tracing/processors.py
index 1b39deda..29eb0f58 100644
--- a/src/agents/tracing/processors.py
+++ b/src/agents/tracing/processors.py
@@ -5,6 +5,7 @@
 import random
 import threading
 import time
+from functools import cached_property
 from typing import Any
 
 import httpx
@@ -50,9 +51,9 @@ def __init__(
             base_delay: Base delay (in seconds) for the first backoff.
             max_delay: Maximum delay (in seconds) for backoff growth.
         """
-        self.api_key = api_key or os.environ.get("OPENAI_API_KEY")
-        self.organization = organization or os.environ.get("OPENAI_ORG_ID")
-        self.project = project or os.environ.get("OPENAI_PROJECT_ID")
+        self._api_key = api_key
+        self._organization = organization
+        self._project = project
         self.endpoint = endpoint
         self.max_retries = max_retries
         self.base_delay = base_delay
@@ -68,8 +69,22 @@ def set_api_key(self, api_key: str):
             api_key: The OpenAI API key to use. This is the same key used by the OpenAI Python
                 client.
         """
+        # We're specifically setting the underlying cached property as well
+        self._api_key = api_key
         self.api_key = api_key
 
+    @cached_property
+    def api_key(self):
+        return self._api_key or os.environ.get("OPENAI_API_KEY")
+
+    @cached_property
+    def organization(self):
+        return self._organization or os.environ.get("OPENAI_ORG_ID")
+
+    @cached_property
+    def project(self):
+        return self._project or os.environ.get("OPENAI_PROJECT_ID")
+
     def export(self, items: list[Trace | Span[Any]]) -> None:
         if not items:
             return
diff --git a/tests/tracing/test_processor_api_key.py b/tests/tracing/test_processor_api_key.py
new file mode 100644
index 00000000..b0a0218a
--- /dev/null
+++ b/tests/tracing/test_processor_api_key.py
@@ -0,0 +1,27 @@
+import pytest
+
+from agents.tracing.processors import BackendSpanExporter
+
+
+@pytest.mark.asyncio
+async def test_processor_api_key(monkeypatch):
+    # If the API key is not set, it should be None
+    monkeypatch.delenv("OPENAI_API_KEY", None)
+    processor = BackendSpanExporter()
+    assert processor.api_key is None
+
+    # If we set it afterwards, it should be the new value
+    processor.set_api_key("test_api_key")
+    assert processor.api_key == "test_api_key"
+
+
+@pytest.mark.asyncio
+async def test_processor_api_key_from_env(monkeypatch):
+    # If the API key is not set at creation time but set before access time, it should be the new
+    # value
+    monkeypatch.delenv("OPENAI_API_KEY", None)
+    processor = BackendSpanExporter()
+
+    # If we set it afterwards, it should be the new value
+    monkeypatch.setenv("OPENAI_API_KEY", "foo_bar_123")
+    assert processor.api_key == "foo_bar_123"