Although national service programs such as AmeriCorps share many characteristics with volunteerism (such as sustained, prosocial action aimed at community improvement), little research has examined how theory and research relevant to volunteer behavior might help understand such service programs. We used psychological theory from the volunteerism literature to test hypotheses about how the constructs of altruistic personality, role identity, and service motivations relate to AmeriCorps satisfaction, intentions, and behavior. In a longitudinal study of 188 AmeriCorps members, personality, identity, and motivation were all associated with important service experiences and outcomes. Specifically, whereas overall motivation was related to both satisfaction and intentions, altruistic personality and AmeriCorps identity were only related to intentions. Additionally, distinct service motivations were related to specific service experiences and outcomes. Finally, AmeriCorps members who felt that their motivations were satisfied during service tended to more frequently engage in additional voluntary service-related behaviors. We discuss implications of these findings for understanding AmeriCorps service, and for potentially improving public policy initiatives concerning AmeriCorps.