Adolescent substance use occurs within a rapidly changing social and environmental context. Prevention programs need to remain relevant and engaging for young people and include their perspective. The Climate Schools: Alcohol and Cannabis online prevention program was co-designed with adolescents in 2007 and has demonstrated its effectiveness in previous randomised controlled trials. Eleven years on, the current study conducted two focus groups with adolescents who had received the Climate Schools program, to obtain feedback regarding the acceptability and relatability of the program. A mixed-methods design (including a written questionnaire and class discussion) was employed to collect both quantitative and qualitative data from participants and an inductive analysis was undertaken to extract major themes. Participants reported an appreciation for the delivery mode (i.e., visual learning style and online platform) and said their knowledge of alcohol and cannabis had improved following the program. Participants also provided suggestions for increasing the relatability of the language and the characters by providing additional backstories and increasing the level of engagement with the program by reducing the length of individual lessons. The feedback obtained in this investigation will be instrumental in the refinement and future development of the Climate Schools program. More broadly, this study reinforces the importance of co-design and revision of substance misuse prevention programs, to ensure their continued engagement and efficacy.