Understanding how to attract and maintain volunteers is crucial for the operation of victim support organizations. We propose that volunteerism can be understood in a similar way as collective action. Active (N = 99) and nominal supporters (N = 134) completed measures of identities (personal, social, and organizational), emotions (sympathy, outrage, and pride), and efficacy beliefs (self-, group, and organizational). The results revealed a different pattern of predictors of volunteerism for the two samples. Among nominal supporters, commitment to volunteerism was predicted by personal identity (“I”), sympathy, and self-efficacy; among the actively engaged, volunteerism was predicted by social identity (“we”), outrage, and self-efficacy. These results suggest that engagement with volunteerism is associated with qualitatively different processes for those nominally versus actively supportive of volunteer efforts.