Many forensic psychiatric inpatients have difficulties regulating aggressive behavior. Evidence of effective aggression treatments is limited. We designed and investigated the effectiveness of a transdiagnostic application of a virtual reality aggression prevention training (VRAPT). In this randomized controlled trial at four Dutch forensic psychiatric centers, 128 inpatients with aggressive behavior were randomly assigned to VRAPT (N = 64) or waiting list control group (N = 64). VRAPT consisted of 16 one-hour individual treatment sessions twice a week. Assessments were done at baseline, post-treatment and at 3-month follow-up. Primary outcome measures were aggressive behavior observed by staff and self-reported aggressive behavior. Analysis was by intention to treat. This trial was registered in the Dutch Trial Register (NTR, TC = 6340). Participants were included between 1 March 2017, and 31 December 2018. Compared to waiting list, VRAPT did not significantly decrease in self-reported or observed aggressive behavior (primary outcomes). Hostility, anger control, and non-planning impulsiveness improved significantly in the VRAPT group compared to the control group at post-treatment. Improvements were not maintained at 3-month follow-up. Results suggest that VRAPT does not decrease aggressive behavior in forensic inpatients. However, there are indications that VRAPT temporarily influences anger control skills, impulsivity and hostility.