Mental health issues are increasingly prevalent among secondary school students in Nigerian cities, leading to a critical need for effective interventions. A mixed-methods approach was employed including pre- and post-training surveys, focus groups, and interviews with teachers and students. The MHFA programme was implemented in four urban schools over a period of six months. MHFA training demonstrated significant improvements in self-reported mental health outcomes among participants, with a notable increase in the proportion of students who felt equipped to support their peers (from 35% to 60%). The MHFA programme was effective in enhancing students' awareness and confidence in recognising mental health issues and providing initial support. Further research should explore long-term effects and implementation strategies, while integrating MHFA training into school curricula for broader impact.