© 2018 Elsevier B.V. Psychopathy is a cluster of personality traits associated with high rates of aggression. While research on psychopathic traits largely focuses on neurobiological factors implicated in aggression, other research suggests that contextual factors, such as social exclusion, also contribute to promoting aggression. Yet, the relationships among psychopathic traits, neural processing of exclusion, and aggression remain unknown. A sample of 76 adolescents and young adults completed Cyberball, a task involving conditions of social inclusion, ambiguous exclusion, and unambiguous exclusion. During Cyberball, a slow wave (SW) event-related potential (an index of elaborative processing) and self-reported anger were measured. Additionally, acts of real-world aggression were assessed. Results indicated that as psychopathic traits increased, SW during ambiguous exclusion also increased, but SW during inclusion decreased. However, the combination of smaller SW during ambiguous exclusion and higher psychopathic traits predicted heightened anger following Cyberball and more frequent real-world aggression. This response to social exclusion among individuals with elevated psychopathic traits may represent an unreflective, reactive style that exacerbates anger and aggression in certain contexts. These data suggest that neurobiological dysfunction in elaborative processing is related to psychopathic traits, and social context comprises another important influence on the aggression of individuals with elevated psychopathic traits.