This study examined developmental and socioeconomic status (SES) differences in young children's altruistic behavior in the dictator game (DG). Children aged 4, 6, and 9 years old from six British primary schools played the DG with genetically unrelated individuals using stickers as resource. Results demonstrated that older children and children from higher SES environments behaved more altruistically, although the majority of children displayed altruistic behavior even at the youngest age level. Results buttress conclusions based on studies from diverse cultures and from brain imaging research by providing additional evidence for the fundamental nature of altruistic behavior, as well as for the probable influence of local socialization practices on development.