Despite its prevalence, chronicity, and clinical impact few clinical trials have evaluated the efficacy of psychotherapy for Intermittent Explosive Disorder (IED). In this randomized clinical trial, participants with IED completed twelve 50-minute individual sessions of either a multi-component cognitive behavioral intervention for IED (n=19) or a time equated supportive psychotherapy (n=25). At baseline, post-treatment and three-month follow-up, all participants received the Overt Aggression Scale–Modified. During these visits, participants also completed self-report measures of relational aggression, anger, cognitive biases, and associated symptoms. Primary study outcomes were aggressive behavior and anger. Though participants in both treatments tended to improve over time, the cognitive behavioral intervention was superior to supportive psychotherapy in decreasing aggressive behavior and relational aggression. These findings support the efficacy of a multi-component cognitive behavioral intervention in treating aggression in IED.