When tested appropriately, infants appear to demonstrate false-belief understanding in the first year of life. Some have argued that this is inconsistent with the well-established relationship between social experience and preschoolers’ false-belief performance. We argue that these two sets of findings are not inconsistent because the ability to attribute false beliefs to others is necessary but not sufficient for false-belief performance, and we propose several ways that one social factor, hearing and using mental-state language, might relate to false-belief performance throughout the lifespan. We tested this account by examining the relationship between adults’ use of mental-state language and their false-belief understanding. Participants’ use of mental-state language was related to how quickly they could accurately predict the behavior of agents on the basis of desires and beliefs. These findings provide the first evidence that mental-state talk and false-belief performance are related into adulthood.