Harris continued his father's successful art dealing business, and was an essentially amateur artist himself. Harris had an important collection of Spanish prints, especially those of Goya, which was mostly acquired by the British Museum after his death. In fact, Harris, while still alive, had placed his collection on indefinite loan in the British Museum. The British Museum has 708 objects formerly in his collection, including 22 prints he made himself, and in 1981 published Juliet Wilson Bareau's, "Goya's Prints, The Tomás Harris Collection in the British Museum".