When World War I broke out, Bates was involved in organizing relief efforts. His father was vice chairman of the vice chairman of the American Commission for Relief in Belgium, while he was a member of the executive committee of the London board. In 1915, he was planning on going to Belgium to help the Commission and boarded the RMS Lusitania, where he was a first class passenger. He was on deck with Amy Lea Pearl, a friend of his, when the ship was struck. He spent the last moments prior to the ship sinking helping Amy and her husband Warren find their children. He died with the ship on May 7, 1915. His body was later recovered. He was buried in the Bates Family Cemetery in Hancock, Massachusetts.