Extracurricular participation in adolescence is often linked to the development of a prosocial identity and social relationships. Through these social psychological mechanisms, participation is thought to prevent risky behavior in adolescence and into emerging adulthood. This study examined the relationship between high school activity portfolios and risky behaviors (i.e. binge drinking, drug use, and law violation) among a college sample. Five activity portfolios were identified, including sports-focused, low involvement, highly engaged, and two combination portfolios. There were significant differences between portfolios on social psychological measures (e.g. prosocial beliefs and social responsibility), current extracurricular involvement, and risky behaviors. Regression models indicated that social psychological factors and current involvement partially mediated the association between portfolios and risky behaviors, but portfolio type retained direct effects. Portfolios associated with involvement across several activity domains were more protective for emerging adults, in part by shaping their beliefs, sense of social responsibility, and continuing involvement