Background Developing low-cost yet scalable interventions for youth depression and anxiety symptoms in low-income regions such as countries in Sub Saharan Africa is a global mental health priority. We developed and intend to evaluate one such intervention for adolescent depression and anxiety in Kenya. The intervention, named Shamiri (a Swahili word for ‘thrive’), draws upon evidence-based components of brief interventions that involve nonclinical principles rather than treatment of psychopathology (e.g. growth mindset, gratitude and virtues). Methods Between 400 and 500 high-symptom Kenyan adolescents (ages 13-18) will be randomized to either the four-week Shamiri group intervention or a group study-skills control intervention of equal duration and dosage. Participating adolescents will meet in groups of 8-15, led by a high-school graduate trained to deliver Shamiri as a lay-provider. Adolescents will self-report primary outcome measures (depression and anxiety symptoms) and secondary outcome measures (e.g., perceived social support, perceived academic control, self-reported optimism, etc.) at the 2-week intervention midpoint, 4-week post-intervention endpoint, and 2-week post-intervention follow-up. We predict that adolescents in the Shamiri group, when compared to the study-skills control group, will show greater improvements in primary outcomes and secondary outcomes. Discussion Results may suggest that a brief, lay-provider delivered, school-based intervention may reduce internalizing symptoms, improve academic outcomes and other psychosocial outcomes in high-symptom adolescents in Sub-Saharan Africa. Trial Registration Pan African Clinical Trials Registry. Trial ID: PACTR201906525818462. Registered 12th June 2019. https://pactr.samrc.ac.za/TrialDisplay.aspx?TrialID=8185