Sam doesn't appear to be married, but he is in a relationship with Oliver Mulherin, an Australian programmer. The two first appeared in public together at a White House event in early 2023, which was a state dinner for Indian Prime Minister Narendra Modhi. Oliver got his degree in programming from the University of Melbourne and has worked on a number of AI and AI-adjacent projects over the course of his career.

In an interview published in New York Magazine in September, Sam explained that he and Oliver live together in a house in the Russian Hills neighborhood of San Francisco during the week. On the weekends, they retreat to a remodeled house in Napa Valley. Sam also said that he's a vegetarian, but that Oliver "likes cows," and the two are thinking about starting a family together soon.

Prior to his relationship with Oliver, Sam was in a relationship with Nick Silvo, whom he met while attending Stanford University. The two were together for almost nine years beginning in college. They planned to get married, but wound up breaking up in 2012, even as the company that they launched together was achieving more success.