Aggressive behaviour is causing a wide range of problems for victims, offenders and the society. Given the current trend to prefer outpatient interventions over residential treatment, and the high treatment drop-out rates in forensic populations, further improvement of the effectiveness of forensic outpatient treatment methods is needed. In this, biofeedback – informing psychiatric patients about their physiological state – is a promising intervention. Real-time biofeedback is expected to help patients to signal heightened arousal in response to emotional events in an early stage. By strengthening physiological awareness and supporting use of prevention skills, we suppose that biofeedback can aid to reduce aggressive behaviour.