Existing economic models of prosociality have been rather silent in terms of proximate psychological mechanisms. We nevertheless identify the psychologically most informed accounts and offer a critical discussion of their hypotheses for the proximate psychological explanations. Based on convergent evidence from several fields of research, we argue that there nevertheless is a more plausible alternative proximate account available: the social motivation hypothesis. The hypothesis represents a more basic explanation of the appeal of prosocial behavior, which is in terms of anticipated social rewards. We also argue in favor of our own social motivation hypothesis over Robert Sugden’s fellow-feeling account (due originally to Adam Smith). We suggest that social motivation not only stands as a proximate account in its own right but also provides a plausible scaffold for other more sophisticated motivations (e.g., fellow-feelings). We conclude by discussing some possible implications of the social motivation hypothesis on existing modeling practice.