Theory of Mind—the ability to infer others’ mental states—is a fundamental part of human social cognition. For decades, researchers have studied whether nonhuman primates have similar representational capacities. While the majority of studies investigating nonhuman primate Theory of Mind have been conducted with captive populations, this review focuses on the insights gained from work with two naturally-living populations: rhesus macaques (Macaca mulatta) at the Cayo Santiago research station and chimpanzees (Pan troglodytes) in Budongo Forest. Not only have these two populations provided further evidence that nonhuman primates track the mental states of other agents, but they have improved our understanding of the representational differences between human and nonhuman Theory of Mind, specifically in cases that involve tracking the perspective of others. Future work with these and other non-captive populations should take advantage of the breadth of nonhuman primate social behaviors to delve into the nuances of their Theory of Mind.