Aim: The aim of this study was to analyse experiences of a health promotion intervention implemented by the Therapeutic and Educational Unit at Villabona prison in Spain, which aimed to create drug-free spaces as part of a model of social rehabilitation. Design: As part of a larger participatory evaluation study concerning the efficacy of community education, qualitative data were collected from inmates and key informants associated with the unit. Methodology: Information was gathered from 68 informants via 32 in-depth interviews, 6 discussion groups and 4 life stories. Participants included 39 inmates, 10 prison professionals, 5 ex-prisoners, 11 stakeholders and 3 family members. Results: The unit provides a drug-free space that encourages healthy behaviours and strengthens formal and informal social ties to enhance protective factors. Conclusion: The educational and therapeutic model employed may provide a successful methodology for the promotion of health in penal system institutions. Drug-free opportunities to promote good health may be provided through inmates' participation in therapeutic spaces and the process of change, alongside effective social and community support. The intervention described here offers a successful new social model of health promotion and education for prison inmates.