Abstract To maintain and develop close relationships, people need to accurately represent the minds of their social partners. Although studies have characterized many aspects of children’s intuitive theory of the mind and children’s intuitive theory of relationships, it is largely unknown whether and how children think about mental state reasoning within relationships. In three experiments, we asked whether children think accurate mental state reasoning is a cue to social closeness. In Experiment 1 (n = 145), we found that 5- to 9-year-old children, but not 4-year-old children, inferred that characters who engage in affective touch (making physical contact, as though nuzzling, while moving together in synchrony) are socially closer and know about each other’s goals and desires. In Experiment 2 (n = 137), we found that 6- to 9-year-old children, but not younger children, inferred that characters who are correct about each other’s minds are socially close. Children did not think...