The Climate Schools: Ecstasy module is a universal harm-minimisation school-based prevention program for adolescents aged 14 to 16 years. The program was developed to address the need for Ecstasy prevention given the increasing use of Ecstasy use among young Australians. The core content of the program is delivered over the Internet using cartoon storylines to engage students, and the teacher-driven activities reinforce the core information. The three-lesson program is embedded within the school health curriculum and is easy to implement with minimal teacher training required. The program was developed in 2010 through extensive collaboration with students (n = 8), teachers (n = 10) and health professionals (n = 10) in Sydney, Australia. This article describes the formative research and process of planning that formed the development of the program and the evidence base underpinning the approach.