The willingness of humans to engage in third-party punishment (TPP)-a lynchpin of our society-critically depends on the interaction between the wrongdoer's intent and the harm that he caused. But what compels us to punish such individuals when we are unaffected by their harms? Inconsistent with the idealized notion that TPP decisions are based on purely cognitive reasoning, intended harmful acts elicit strong emotional reactions in third-party decision makers. While these emotional responses are now believed to be a driving force in TPP decision making, there is debate about what emotions may be motivating this behavior. Here we show that-unlike anger, contempt, and disgust-moral outrage is evoked by the integration of culpable intent and severe harm, and that the expression of moral outrage alone mediates the relationship between this integrative process and punishment decisions. Sadness had the opposite effect of dampening punishment in response to accidental harms. We take these findings to indicate that moral outrage expresses the interaction of intent and harm in driving third-party punishment behavior. (PsycInfo Database Record (c) 2022 APA, all rights reserved).