Nairobi public schools have a high prevalence of adolescent depression, underscoring the need for effective mental health interventions. A mixed-methods approach was employed, including pre- and post-intervention assessments with a control group for comparison. The analysis revealed that the intervention significantly reduced depressive symptoms by 25% among participants compared to baseline levels. School-based mental health interventions show promise in reducing adolescent depression in Nairobi's public schools, warranting further implementation and evaluation. Policy makers should prioritise funding for school-based mental health programmes and advocate for their integration into existing educational frameworks.