Overweight youth are often socially marginalized and have fewer friends than their nonoverweight peers. Participation in organized activities may be one way to promote friendships for overweight youth. In this study, we used a large nationally representative sample to test whether two aspects of participation promoted friendships, namely the number of activities and the social acceptance of activity co-participants. In contradiction to our hypotheses, participating in activities with high socially accepted peers was associated with significantly "fewer" friendships over time for overweight adolescents. Conversely, there were small differences between overweight and nonoverweight adolescents' friendships when they participated in activities with low socially accepted co-participants. Our findings provide new insight that activities may not be universally beneficial for overweight adolescents' peer relationships. We discuss the various peer mechanisms that explain why certain types of activities predict these friendship patterns for overweight youth.