Patients with a co-occurring substance use disorder and other mental disorder (dual diagnosis) are at increased risk of victimization: to become victims of for instance physical abuse, sexual abuse, and property crimes.<br/> AIM: To examine the effectiveness of the sos training: a new group-based intervention to improve resilience of dual diagnosis patients and thereby reduce their risk of victimization.<br/> METHOD: A randomized controlled trial was conducted in dual diagnosis patients, with a 14-month follow-up period. Patients were randomized to receive either care as usual (n = 125), or care as usual plus sos training (n =125). The primary outcome measure was defined as treatment response for victimization (yes/no), with 'yes' defined as at least a 50% reduction in the number of past-year victimization incidents at 14-month follow-up compared to baseline.<br/> RESULTS: Significantly more participants in the experimental group achieved positive treatment response for victimization (68%) compared to the control group (54%).<br/> CONCLUSION: Adding sos training to care as usual in dual diagnosis patients is more effective in reducing victimization compared to care as usual alone. The sos training can be implemented in addiction-psychiatry services to prevent future victimization in these patients.