Background Depending on the exposure to traumatic stressors and combat, 20% to 50% of ex‐combatants present with trauma‐related disorders, and more than half of the members of armed groups have a proclivity to violence. Therefore, psychotherapeutic assistance should address both, trauma‐related suffering and the lowered threshold for aggressive behaviour. Objective Supporting the demobilization process of ex‐combatants in the eastern DR‐Congo, we implemented a version of Narrative Exposure Therapy adapted for Forensic Offender Rehabilitation (FORNET). Method In two successive dissemination stages (DS), local counsellors conducted FORNET. In DS1, they were trained by clinical experts, and in DS2, the by then experienced counsellors trained and supervised a second group of local counsellors (DS2). The training consisted of a 3‐week workshop covering theoretical concepts and practical therapeutic skills. In DS1 and DS2, a total of 98 demobilizing combatants received an intervention; treatment‐as‐usual served as the control condition. Posttraumatic stress disorder, appetitive aggression, depression severity and drug dependence were assessed prior to the intervention and 6 and 12 months later; additionally, we assessed reintegration success. Results Six months post‐intervention, FORNET significantly reduced Posttraumatic stress disorder symptoms but had less effect on the trait of appetitive aggression; moreover, beneficial effects were found for depression severity and drug dependence as well as for reintegration indices. Treatment gains were retained at 12 months. Conclusions Individuals without previous training in psychotherapy can learn to effectively apply the brief intervention FORNET and support the demobilization process in ongoing conflicts. The study suggests that it is possible to pass down psychotherapeutic techniques over generations of counsellors. © 2015 The Authors. Clinical Psychology & Psychotherapy published by John Wiley & Sons Ltd. Key Practitioner Message Posttraumatic stress symptoms, depression and clinically relevant levels of drug dependence can effectively be reduced with a version of Narrative Exposure Therapy (NET) adapted for Forensic Offender Rehabilitation (FORNET). The intervention is effective in the context of ongoing conflict. Individuals without previous training in psychotherapy can learn to effectively apply the brief intervention FORNET. It is possible to pass down psychotherapeutic techniques like FORNET over generations of counsellors. Psychotherapeutic interventions like FORNET may facilitate the transition to peace in war‐torn regions.