This study examined (a) the unique contribution of mothers' involvement in their children's organized activity, fathers' involvement in the activity, social integration in the activity peer group, and social support from the activity leader on youth adjustment and (b) the moderating effects of youths' gender and prior adjustment on these associations. The dimensions of adjustment included academic achievement, problem behaviors, depressive symptoms, and persistence of participation. Study participants were 115 youths (59% girls; X = 13.39). Participation in organized activities and the interpersonal relationships within these activities were assessed in the 7th grade. The dimensions of adjustment were measured both in Grades 6 and 7. Altogether, the findings revealed few main effects of the activity-related interpersonal relationships on youth adjustment. Rather, the results highlighted that boys and youths with prior difficulties were especially sensitive to the interpersonal components of their activity participation. (Contains 1 figure, 2 tables and 1 note.)