diff --git a/google/auth/transport/requests.py b/google/auth/transport/requests.py
index a55b5f57b..2805375b8 100644
--- a/google/auth/transport/requests.py
+++ b/google/auth/transport/requests.py
@@ -149,6 +149,10 @@ def __init__(self, session=None):
 
         self.session = session
 
+    def __del__(self):
+        if hasattr(self, 'session') and self.session is not None:
+            self.session.close()
+
     def __call__(
         self,
         url,
diff --git a/google/auth/transport/urllib3.py b/google/auth/transport/urllib3.py
index ad67327a4..fd14f8873 100644
--- a/google/auth/transport/urllib3.py
+++ b/google/auth/transport/urllib3.py
@@ -427,6 +427,10 @@ def __exit__(self, exc_type, exc_val, exc_tb):
         """Proxy to ``self.http``."""
         return self.http.__exit__(exc_type, exc_val, exc_tb)
 
+    def __del__(self):
+        if hasattr(self, 'http') and self.http is not None:
+            self.http.clear()
+
     @property
     def headers(self):
         """Proxy to ``self.http``."""