We tested a trauma-focused, cognitive–behavior therapy treatment (TF-CBT-anger) for intermittent explosive disorder (IED) and related dimensions of anger adapted to the local culture in postconflict Timor-Leste. The intention-to-treat sample (n = 78) comprised Timorese nationals (women = 49; men = 29), ages 18 years and older, meeting Diagnostic and Statistical Manual of Mental Disorders (4th ed.) criteria for IED, with equal numbers (n = 39 each) being randomized to the treatment group (TG) and wait-list (WL). Assessments were made at 1 week prior to therapy, immediately at posttreatment, and at 1 month follow-up. Primary measures included an IED diagnosis made according to the East Timor explosive anger measure and the directionality of expression and control of anger assessed by 4 dimensions of the State–Trait Anger Expression Inventory (STAXI-2). Secondary measures included psychological distress assessed using the Kessler scale and an index of posttraumatic stress disorder (PTSD) assessed using the Harvard Trauma Questionnaire. In the TG, there was a decline in IED from 100% to zero at follow-up. In the WL, more than 70% (of the 100% at baseline) showed persisting IED at second and third assessments. The TG alone showed significant (p < .05) improvements on all STAXI-2 scales, the effect sizes for the intervention being uniformly large (>0.80). Psychological distress and PTSD showed substantial reductions in the TG but not the WL group. Although based on a modest-sized sample, our findings provide the first evidence in support of the efficacy of TF-CBT-anger for IED in a culturally diverse, postconflict setting.