It is said that the friendship between Saionji, who attended the post World War I Paris Peace Conference (1919) as the envoy plenipotentiary of Japan, and his best friend Clemenceau, who stayed at the same boarding house as Saionji when he studied in Paris, was very instrumental in securing Japan's position at the Peace Conference.
なお、第一次世界大戦後のパリ講和会議（1919年）に日本の全権特使として出席した西園寺とパリ留学時代を同じ下宿ですごした親友クレマンソーとの友情は、講和会議での日本の立場を保持するのに大いに役立ったと伝えられる。