In Lagos, Nigeria's largest city, secondary school dropout rates remain a significant concern among policymakers and educators. The study employed action research to design, implement, and evaluate a peer-mentoring programme targeting selected Lagos secondary schools. Data were collected through pre-and post-programme surveys, interviews, and focus group discussions among students, mentors, and school administrators. A notable trend indicated that the dropout rate decreased by 25% in schools where peer-mentoring was implemented compared to those without a programme. Peer-mentoring programmes appear effective in mitigating dropout risks among secondary students in Lagos. This study offers insights into their implementation and potential benefits for educational policy development. Lagos education authorities should consider scaling up the peer-mentoring model to more schools based on this study's findings, with a focus on enhancing mentor training and student support services.