In 1911, Trumbull was engaged to the painter Katherine Sophie Dreier, when they both lived in London. In August 1911, he married Dreier at her home at 6 Montague Terrace in Brooklyn. Shortly after the marriage ceremony, Dreier found out that he was already married as Trumbull's existing betrothal had not come to a legal conclusion. Trumbull and Dreier's marriage was thus annulled.