Introduction: This study tested the feasibility and preliminary efficacy of Coping and Emotional Development for Adolescents to Reduce Stress (CEDARS) a positive psychological intervention (PPI), tailored for adolescents and administered in a classroom setting, in boosting CEDARS skill use and emotional well-being. Method: Adolescents (N = 102, 45% female) aged 13-15, in four physical education classes at the same school were randomly assigned by classroom to either receive the CEDARS intervention (n = 59) or engage in the usual class activities (n = 44). Participants completed self-report measures at three time points assessing use of intervention skills, positive and negative affect, depressive symptoms, and perceived stress. Results and conclusion: Groups differed significantly on race with 57% of the intervention group compared to 75% of the control group identifying as Asian or Pacific Islander. Race-adjusted analyses revealed that both groups improved on intervention skill use, negative affect, depressive symptoms, and perceived stress. The group by time interaction was significant such that the CEDARS group increased skill use from pre- to post- intervention and this difference persisted at follow-up. Contrary to hypotheses, there were also significant group by time interactions indicating that the control group had a steeper decline in depression and perceived stress from pre- to post-intervention. Students reported high acceptability and feasibility and suggested key changes to increase engagement. The current study expands on the existing PPI literature focused on adolescents and highlights the need for larger and more diverse samples, as well as developmentally- and culturally-tailored interventions.