Children construct their social preferences and behaviors based on their social interactions and beliefs about other’s behavior. Most studies that evaluate the influence of social norms on children’s sharing behavior has focused on sharing decisions, while no previous study has evaluated whether norms about generosity could change beliefs about other’s sharing behavior. In the current study, 4–10-year-old children (N = 101) played two dictator games; one as baseline and the other after being exposed to either a generous or a selfish descriptive norm. Our results showed that, after being exposed to descriptive norms, all children changed their beliefs about others’ sharing behavior. However, these norms did not influence children’s sharing decisions. These results suggest that children´s beliefs about sharing behavior could be more malleable than their actual sharing decisions. These insights might help to design interventions aimed to change beliefs and, in turn, to model prosocial behaviors in children.