The contribution of nonfamily adults to young people's well-being was explored using both a cross-sectional national sample of 614 12- to 17-year-olds and a longitudinal sample of 370 students followed from 6th-8th grades through 10th-12th grades. Both variable- and person-centered analyses were employed. Young people's involvement in volunteering, youth programs, and religious organizations was hypothesized to increase the frequency as well as the quality of their relationships with nonfamily adults. Greater community involvement was related to (a) greater and qualitatively different kinds of engagement with nonfamily adults; (b) higher levels of positive developmental processes of support, empowerment, and boundary setting; (c) lower levels of risk behaviors; and (d) higher levels of thriving. The results suggest the utility of positive youth development theory, research, and applications for predicting and enhancing young people's concurrent and longer-term well-being. (Contains 4 tables, 1 figure and 2 footnotes.)