Depression among Nigerian adolescents is a significant public health concern, necessitating effective school-based mental health interventions. A systematic review was conducted using peer-reviewed articles and grey literature published between and , focusing on school-based interventions targeting adolescents with depression. Quantitative data from these studies were analysed to assess the efficacy of the programmes. The analysis revealed a moderate reduction in depressive symptoms among participants who received the intervention compared to controls (p < .05), indicating potential effectiveness but variability across different programme implementations. School-based mental health interventions show promise for mitigating depression in Nigerian adolescents, though further research is needed to optimise and standardise these programmes. Policy makers should prioritise the integration of evidence-based school-based mental health programmes into existing educational frameworks to enhance adolescent mental well-being. Depression, Mental Health Interventions, School-Based Programmes, Nigerian Adolescents