Abstract The argument for targeting adolescent health has been made strongly, with poor lifestyle behaviours often emerging during this life stage. Furthermore, there is consistent evidence of a widening socioeconomic gap in health indicators. Developing health literacy (HL) in youth populations to improve lifelong health behaviours has garnered increased interest in recent years. This process evaluation examines the acceptability, fidelity and dose delivered of the pilot of LifeLab Dublin: a nine-week, school-based HL intervention for low socioeconomic adolescents. The intervention, which comprised of two out-of-school, interactive HL experiences in conjunction with seven school-based lessons, took place between September and December in 2021 and involved students aged 11 - 13. The health issues targeted were previously identified by the teachers and students of the target population, and the learning activities within the out-of-school experiences were co-designed by adolescents of a similar demographic. Overall, the intervention was perceived positively by the students and teachers, particularly the two interactive out-of-school experiences. The teachers, however, highlighted issues with the volume and content of the school-based lessons, resulting in a reduced number of lessons being delivered. The fidelity of the two LifeLab experiences was high, demonstrating that the students engaged well with the learning activities and that the experience aligned with LifeLab’s core principles and underpinning theoretical constructs. The findings from this study highlight the value in implementing experiential style learning in school-based HL education and the benefit of involving participants in the design of intervention. The evaluation provided valuable insight into the refinements required to enhance the efficacy of the intervention, as well as providing an evidence-base to inform future school-based HL interventions for low socioeconomic adolescents. Key messages • The benefit of adopting experiential style health literacy education with young people. • The benefit of including young people in the design of a health literacy intervention.