In this study, we investigated the contribution of organized youth sport to antisocial and prosocial behavior in adolescent athletes. The sample consisted of N=260 male and female soccer players and competitive swimmers, 12 to 18 years of age. Multilevel regression analysis revealed that 8% of the variance in antisocial behavior and 7% of the variance in prosocial behavior could be attributed to characteristics of the sporting environment. Results suggested that coaches who maintain good relationships with their athletes reduce antisocial behavior, and that exposure to relatively high levels of sociomoral reasoning within the immediate context of sporting activities promotes prosocial behavior. These results point to specific aspects of adolescents' participation in sport that can be used to realize the educational potential of organized youth sport. © Springer Science+Business Media, LLC 2007.