Three experiments showed that gratitude positively affected preschool children's prosocial behavior. In the studies, the experimenter induced gratitude by giving a token gift and then making a request for help or to share resources. Experiment 1 (N = 126, 4- to 6-year-olds) showed that gratitude increased helping behaviors toward the benefactor, and that emphasis on the benefactor's intention had a significant effect on helping behaviors. Experiment 2 (N = 129, 4- to 6-year-olds) indicated that grateful emotions increased the likelihood that the children would help not only the benefactor but also a stranger. Experiment 3 (N = 133, 3- to 6-year-olds) showed that gratitude motivated preschoolers' sharing behavior with the benefactor. Children's theory-of-mind and their understanding of the benefactor's intention mediated the relationship between children's age, gratitude, and prosociality.