Objective: This study assessed the effectiveness of an adapted Brief Strategic Family Therapy (BSFT) intervention for gang-affiliated Mexican American adolescents and their parents. Methods: A total of 200 adolescents and their family caregivers were randomized to either a treatment or a control condition. Outcomes included adolescent substance use, conflict resolution, gang identification, parent substance use knowledge, gang awareness, family cohesion, child conduct problems and stress. Participants were assessed at baseline, treatment exit at 16 weeks, and 6 months follow-up. General linear mixed-effects and generalized estimating equations models were used to evaluate between-group differences in outcomes. Results: There were significant differences between the BFST and control groups on adolescent alcohol use at 6 months and parents' reported conduct problems. No impact on marijuana use was found. Conclusions: Results provide emerging evidence supporting the adapted BSFT for gang-affiliated Mexican American adolescents and their families for alcohol and behavioral outcomes. Future adaptations may be needed to reduce drug use. (Contains 3 figures and 3 tables.)