Deering was a gifted amateur artist, and while still in the Navy he used his free time to become acquainted with leading artists and to visit the world's great art galleries. He began a lifelong habit of collecting art, both by acknowledged masters and contemporaries. In 1876, he met the painter John Singer Sargent, who became a close friend. Other artist-friends included sculptor Augustus St. Gaudens, the Swedish artist Anders Zorn, and Catalan artist Ramon Casas i Carbo. In 1893, Deering took time off from his other duties to study painting in Paris under Zorn for an entire season. Throughout his life, Deering enthusiastically supported and championed the work of many living artists while also avidly purchasing hundreds of older, more obscure works along with many acknowledged masterpieces.