Costos lives in Los Angeles, California, with his partner Michael S. Smith. He is a vegetarian, but imposed no dietary restrictions on embassy functions. On the subject of LGBT rights, Costos has said "I am not an Activist. I broadly support human rights for straight, gay, women’s issues. And I just happen to be gay.... This doesn't define me as a person, but it is part of who I am. It's like being a vegetarian: it's one more facet of James Costos." He said he and Smith had been welcomed in Spain "with great accommodation" and that because Spain already provides LGBT civil rights, the role he and Smith played was a symbolic for those who still suffered from a lack of enforcement in support of their rights: "What we can do through our messaging is give a sense of hope."