The e-Intervention Enhancing Mental Health in Adolescents project, IMPROVA, will co-design, pilot, evaluate, and facilitate the upscaling of a modular eHealth intervention platform that aims to improve mental health and well-being, early detect mental health problems and prevent common mental disorders in adolescents. The IMPROVA consortium includes an international and inter-disciplinary group of researchers and practitioners from health, educational and social sciences in addition to computer scientists, a teacher association and policymakers. The IMPROVA online platform will be co-created with stakeholder groups, including adolescents, parents, teachers, school health professionals and policymakers based on materials already designed and tested in more than 20 projects carried out by the consortium members. The platform will include components for adolescents, parents, teachers, and school health professionals in complementary and synergistic modules. After a series of pilot testing sessions, IMPROVA will be implemented by conducting a randomized Stepped Wedge Trial Design (SWTD) in secondary education schools randomly selected in four countries (France, Germany, Romania and Spain), including 12,800 adolescents. Effectiveness, cost-effectiveness and cost-benefit will be calculated. Using implementation science methodology, IMPROVA will co-design with policymakers and stakeholders transferable evidence-based practices, methodologies and guidance for upscaling of the IMPROVA platform. IMPROVA aims to provide stakeholders and policy makers with an evidence-based, innovative, large-scale, comprehensive intervention, and a scale-up plan to promote mental health and prevent mental disorders in adolescents; empower adolescents and families to make better decisions regarding their mental health; and provide schools and the community with tools to achieve a society with better mental health and lower stigma.