Findings indicate that the quality of the interpersonal relationships youths maintain in the context of organized activities can be associated with their adjustment and long-term participation. Positive interpersonal input within activity participation might be especially important in early adolescence, when youths experience multiple transitions in school settings, parent-child relationships, and peer networks. Organized leisure activities are social settings in which youths engage in interpersonal interactions. Even though participating in these activities has generally been linked to positive outcomes, not every youth may benefit from participation. Specifically investigated in this study were the unique contributions of mothers’ and fathers’ involvement in the activity, social integration in the activity peer group, and support from the activity leader to adolescent adjustment. In addition, youths’ gender and prior adjustment were explored as moderators of these associations. The findings revealed few main effects of the interpersonal relationships on youth adjustment; rather, the results highlighted the importance of considering moderators. Data were collected from 390 youths attending 8 elementary schools from 4 distinct districts in the province of Quebec, Canada. Tables, figure, note, and references