This study explored interpersonal and intrapersonal factors associated with the level of autonomous motivation adolescents experience for their after-school activities. A total of 142 seventh-grade adolescents completed measures of peer relatedness, autonomy within friendships, mother and father autonomy support, perceived activity competence, autonomous motivation for their after-school activity, and subjective well-being. Autonomous motivation for after-school activity was associated with greater subjective well-being. Peer relatedness was positively related to adolescents' intrinsic and identified motivation for their after-school activities and inversely related to their introjected motivation, whereas neither mother nor father autonomy support predicted autonomous motivation. Perceived activity competence was also positively associated with intrinsic and identified motivation for after-school activity. Furthermore, autonomy within friendships mediated the relation between peer relatedness and autonomous motivation for after-school activity. Results suggest that peer relationships and perceived competence may have important roles in fostering experiences of autonomy and well-being in adolescence. (Contains 3 tables.)