In two studies of 5th–12th graders (n = 2,371; n = 999), we compare four groups based on engagement patterns in community service (CS) and/or extracurricular activities (EC). In both studies, adolescents who engaged in BOTH CS (whether mandated or voluntary) and EC had the highest reports of bonding and bridging social capital, intergenerational harmony, and social support whereas those who did NEITHER had the lowest. For most outcomes, adolescents engaged only in CS had higher reports than peers engaged only in EC. Content analyses of what adolescents learned in CS suggest its potential for broadening their awareness of fellow members of their communities, their mutual obligations, and collective capacities.