This study reports on the longitudinal analysis of a structured after-school arts program for Canadian youth, ages 9 to 15 years, from low-income communities where the relationship of peer social support, family interactions, and psychosocial outcomes is evaluated. Multi-level growth curve analyses suggest an increase in prosocial development with peer social support and a decrease in prosocial development when negative family interactions are present. Comparisons between matched controls, using estimated linear propensity scores, revealed significant improvement in prosocial behaviors for the intervention group. The structured after-school arts program was found to increase prosocial behaviors and bonding with peers for youth from low-income communities. (Contains 3 tables.)