The negative affect that results from negative feedback is a substantial, proximal cause of aggression. People high in maladaptive perfectionism, the tendency to focus on the discrepancy between one's standards and performance, are characterized by an exaggerated negative affective response to negative feedback. This exacerbated affective response to failure may then dispose them to hurt others and themselves as aggression and self‐harm are often perceived as a means to regulate negative affect. In Study 1, we demonstrated that maladaptive perfectionism was linked to greater aggressive behavior towards others after receiving negative feedback. Suggesting the presence of an emotion regulation strategy, this effect was mediated by the motivation to use aggression to improve mood. In Study 2, maladaptive perfectionism was linked to self‐harm, an effect exacerbated by negative feedback and mediated by negative affect. These findings suggest that maladaptive perfectionists are at risk for greater harm towards others and the self because negative feedback has a stronger affective impact and harming others and the self is perceived a means to alleviate this aversive state. Aggr. Behav. 9999:XX–XX, 2014. © 2014 Wiley Periodicals, Inc.