OBJECTIVE: Effective and scalable interventions to address adolescent depression are urgently needed. This study evaluated the feasibility, acceptability, and preliminary efficacy of digitally delivered Behavioral Activation therapy. METHOD: A pilot randomized controlled trial was conducted in rural northeastern South Africa. Adolescents 15 to 19 years of age with mild-to-moderately severe depression on the Xitsonga version of the Patient Health Questionnaire-Adolescent Version (PHQ-A) were recruited from 11 high schools. Participants were randomly assigned (1:1) to receive the Kuamsha app, which delivers Behavioral Activation therapy through an interactive narrative game with telephone guidance from peer mentors or a control app. We used a mixed-methods design to assess the feasibility, acceptability, and preliminary efficacy of the Kuamsha app in reducing symptoms of depression compared to a digital control. RESULTS: Between April and September 2022, a total of 195 adolescents were randomized. Primary outcome data were available on 195 adolescents (100%). In the Kuamsha group, 77 participants (80.2%) adhered to the treatment protocol (completed at least 4 of 6 app modules), indicating favorable engagement. In-depth interviews and questionnaire responses revealed high acceptability. Reductions in depressive symptoms were modest, with no significant between-group differences at 11 weeks (adjusted mean difference = -0.37, 95% CI = -1.96, 1.22) or 24 weeks (adjusted mean difference = -0.11, 95% CI = -1.70, 1.48). Exploratory analyses suggested greater efficacy among participants who met a cut-off for moderate baseline depression symptoms (PHQ-A ≥10) and greater app engagement. CONCLUSION: The Kuamsha app is a feasible and acceptable treatment for depression among adolescents in rural South Africa. Following adaptations, a larger trial is warranted to assess its effectiveness in reducing symptoms of depression. DIVERSITY & INCLUSION STATEMENT: We worked to ensure sex and gender balance in the recruitment of human participants. We worked to ensure race, ethnic, and/or other types of diversity in the recruitment of human participants. We worked to ensure that the study questionnaires were prepared in an inclusive way. One or more of the authors of this paper self-identifies as a member of one or more historically underrepresented racial and/or ethnic groups in science. One or more of the authors of this paper self-identifies as a member of one or more historically underrepresented sexual and/or gender groups in science. One or more of the authors of this paper self-identifies as living with a disability. We actively worked to promote sex and gender balance in our author group. We actively worked to promote inclusion of historically underrepresented racial and/or ethnic groups in science in our author group. The author list of this paper includes contributors from the location and/or community where the research was conducted who participated in the data collection, design, analysis, and/or interpretation of the work.