Acceptance and commitment therapy programs have rarely been used as preventive tools for alleviating stress and enhancing coping skills among adolescents. This randomized controlled trial examined the efficacy of a novel Finnish web- and mobile-delivered five-week intervention program called Youth COMPASS among a general sample of ninth-grade adolescents (n= 249, 49% females). The intervention group showed a small but significant decrease in overall stress (between-group Cohen’s d = 0.22) and an increase in academic buoyancy (d= 0.27). Academic skills did not influence the intervention gains, but the intervention gains were largest among high-stressed participants. The results suggest that the acceptance and commitment based Youth COMPASS program may be well suited for promoting adolescents’ well-being in the school context.