Service learning in middle school provides opportunities for addressing community needs while also enhancing the social and emotional development of adolescents from vulnerable communities. This longitudinal research study examined the effects of embedding a yearlong service learning program into existing school curricula for young adolescents in a local public middle school setting. The intervention, Wyman’s Teen Outreach Program, was implemented in partnership with the Wyman Center from August 2012 to May 2015. The study used mixed methods to understand how service learning affects student and school-level beliefs and developmental outcomes, especially for students who are vulnerable to academic and disciplinary difficulties. Students in the intervention participated in a weekly positive youth development curriculum and 20 hours of student-led service learning projects per year. Student-level outcomes were measured using surveys that gauged school, neighborhood, and community belonging; academic engagement and efficacy; and civic duty and participation.