Background <p>Strengthening social and emotional competencies (SECs) is a promising upstream strategy for adolescent suicide prevention. However, the existing school-based programmes cannot be directly transplanted into the Chinese school environment. It could be attributed to the different psychosocial challenges faced by adolescents, educational structures, and implementation constraints in China. To address this gap, this study developed a culturally adapted, teacher-delivered, school-based mental health promotion programme to enhance adolescents’ SECs and support suicide prevention in China.</p> Methods <p>This study involved a needs assessment and pilot implementation to inform the development of a school-based mental health promotion programme. Drawing on these preliminary findings, two rounds of Delphi consultations were conducted to assess the programme. The experts assessed the importance and appropriateness of the core modules and sessions, as well as the feasibility of the standardised session structure and teacher training strategies. In both Delphi rounds, the experts independently rated each item on a five-point Likert scale (1–5) and provided open-ended comments. For each item, consensus was defined as a mean score ≥ 4.0, a coefficient of variation (CV) ≤ 0.25, and an agreement rate of ≥ 80%. A total of 25 experts participated in the evaluation, including psychiatrists and child and adolescent clinical and educational psychologists.</p> Results <p>The final programme comprised three parts: core modules and sessions, session structure, and teacher training strategies. The five modules—emotion regulation, interpersonal relationships, self-confidence, resilience, and crisis prevention—consisted of 25 sessions (45&#xa0;min each). Each session was structured into seven steps: warm-up; theme introduction; boundaries and rules in discussion; scenario presentation; group discussion; summarisation and feedback; and emotional relief, if necessary. The training strategies for teachers consisted of instructive lectures on key points, core modules, and sessions of the proposed programme; demonstration of proposed sessions; on-site supervision of sessions conducted by trained teachers; online discussion and communication; and continued feedback and encouragement.</p> Conclusion <p>This study developed a teacher-delivered, school-based mental health promotion programme for adolescents in China. The proposed programme is culturally adaptable, has the potential to be integrated into routine school practices, and holds promise for supporting adolescent suicide prevention.</p>