Despite increased depression in adolescents with Autism Spectrum Disorder (ASD), effective prevention approaches for this population are limited. A mixed methods pilot randomised controlled trial (N = 29) of the evidence-based Resourceful Adolescent Program-Autism Spectrum Disorder (RAP-A-ASD) designed to prevent depression was conducted in schools with adolescents with ASD in years 6 and 7. Quantitative results showed significant intervention effects on parent reports of adolescent coping self-efficacy (maintained at 6 month follow-up) but no effect on depressive symptoms or mental health. Qualitative outcomes reflected perceived improvements from the intervention for adolescents’ coping self-efficacy, self-confidence, social skills, and affect regulation. Converging results remain encouraging given this population’s difficulties coping with adversity, managing emotions and interacting socially which strongly influence developmental outcomes.