BACKGROUND: Schools can play an important role in health promotion by improving students' health literacy, attitudes, health-related behaviours, social connection and self-efficacy. These interventions can be particularly valuable in low- and middle-income countries with low health literacy and high burden of disease. However, the existing literature provides poor guidance for the implementation of school-based interventions in low-resource settings. This paper describes the development and pilot testing of a multicomponent school-based health promotion intervention for adolescents in 75 government-run secondary schools in Bihar, India. METHOD: The intervention was developed in three stages: evidence review of the content and delivery of effective school health interventions; formative research to contextualize the proposed content and delivery, involving intervention development workshops with experts, teachers and students and content analysis of intervention manuals; and pilot testing in situ to optimize its feasibility and acceptability. RESULTS: The three-stage process defined the intervention elements, refining their content and format of delivery. This intervention focused on promoting social skills among adolescents, engaging adolescents in school decision making, providing factual information, and enhancing their problem-solving skills. Specific intervention strategies were delivered at three levels (whole school, student group, and individual counselling) by either a trained teacher or a lay counsellor. The pilot study, in 50 schools, demonstrated generally good acceptability and feasibility of the intervention, though the coverage of intervention activities was lower in the teacher delivery schools due to competing teaching commitments, the participation of male students was lower than that of females, and one school dropped out because of concerns regarding the reproductive and sexual health content of the intervention. CONCLUSION: This SEHER approach provides a framework for adolescent health promotion in secondary schools in low-resource settings. We are now using a cluster-randomized trial to evaluate its effectiveness and cost-effectiveness.