Online communities have become a major medium for social interaction amongst Internet users. However, communities addressing similar topics often have a considerable overlap in resources, which makes them at least partial substitutes for each other. Given the ease with which these resources can be accessed, why would individuals choose to return repeatedly to one community, and indeed go on to invest additional time and energy in doing the voluntary work necessary to keep that community going? We draw on organizational commitment theory to propose an integrated framework for understanding why community members perform three essential kinds of voluntary behaviors – community citizenship behaviors, content provision, and audience engagement. Commitment theory argues that three kinds of bonds (affect-based, norm-based, and cost-based) may form between individuals and organizations, and we adapt this theory to an online community context. Our results indicate that each form of commitment has a contrasting influence on members’ performance of voluntary behaviors in the community. Community citizenship behaviors are driven by affective and normative commitment, content provision by affective and continuance commitment, and audience engagement by continuance commitment alone. Using this established theoretical framework allows us to model and simultaneously test a range of motivations, thereby producing a more integrated perspective that offers greater precision in predicting a variety of important online behaviors.