Supporting one's family is a major reason why many people work, yet surprisingly little research has examined the implications of family motivation. Drawing on theories of prosocial motivation and action identification, we propose that family motivation increases job performance by enhancing energy and reducing stress, and it is especially important when intrinsic motivation is lacking. Survey and diary data collected across multiple time points in a Mexican maquiladora generally support our model. Specifically, we find that family motivation enhances job performance when intrinsic motivation is low—in part by providing energy, but not by reducing stress. We conclude that supporting a family provides a powerful source of motivation that can boost performance in the workplace, offering meaningful implications for research on motivation and the dynamics of work and family engagement.