This study sought to describe religiosity and denominational affiliation among the U.S. population living with HIV and to test whether either is associated with HIV-related sexual risk behaviors. A nationally representative sample of 1,421 people in care for HIV, 932 of whom reported recent sexual activity, was utilized. Religiosity was associated with fewer sexual partners and a lower likelihood of engaging in unprotected sex and in high-risk sex. Catholics were less likely to report unprotected sex than were other Christians, adherents of non-Christian religions, and those reporting no religious affiliation. Catholics were also less likely than other Christians to report high-risk sex and reported fewer sexual partners compared to those of non-Christian religions. We did not observe a difference between Catholics and Evangelicals in the three sexual behaviors investigated. Results suggest that religiosity and some religious teachings may promote safer sex among people with HIV.