The present study examined the relationship between participation in sports during adolescence and physical activity and subjective health in young adulthood. A sample of 8,152 (males = 50.8%, females = 49.2%) adolescents from the National Longitudinal Study of Adolescent Health were used. Results of the study showed that participating in an organized sport during adolescence was associated with higher levels of physical activity and better subjective health during young adulthood after controlling for participation in general physical activities (e.g., jogging, biking, skateboarding) during adolescence. Participation in sports during adolescence was associated with more positive self-beliefs 1 year later that, in turn, were associated with higher levels of moderate to vigorous physical activity and better subjective health 6 years later. Results suggest that positive self-beliefs partially mediate the relationship between adolescents' participation in sports and two health outcomes in young adulthood: moderate to vigorous physical activity and subjective health. Findings highlight the utility of youths' participation in organized sports for promoting healthy outcomes. Implications for policy and practice are discussed.