People typically explain others’ behaviors by attributing them to the beliefs and motives of an unobservable mind. Although such attributional inferences are critical for understanding the social world, it is unclear whether they rely on processes distinct from those used to understand the nonsocial world. In the present study, we used functional MRI to identify brain regions associated with making attributions about social and nonsocial situations. Attributions in both domains activated a common set of brain regions, and individual differences in the domain-specific recruitment of one of these regions—the dorsomedial prefrontal cortex (DMPFC)—correlated with attributional accuracy in each domain. Overall, however, the DMPFC showed greater activation for attributions about social than about nonsocial situations, and this selective response to the social domain was greatest in participants who reported the highest levels of social expertise. We conclude that folk explanations of behavior are an expert use of a domain-general cognitive ability