Purpose The sexual health of the male prison population is often among the poorest in a country. This paper aims to identify the wider health impacts and social value of a sexual health self-sampling programme offered to male prisoners in an open prison setting in Wales. Design/methodology/approach This study applied a unique pilot approach of using Health Impact Assessment and Social Return on Investment Frameworks in tandem. Key stakeholder groups affected by the intervention were identified, and engaged with through workshops, interviews and questionnaires to identify and quantify the health impacts and wider outcomes. Outcomes were then valued using proxy financial values to present the overall estimated social value of the self-sampling service. Findings Based on a small sample, results indicate that for every £1 spent on the self-sampling service in the prison, a potential value of £4.14 was created. This resulted in a ratio of £4.14:£1. Approximately one-third of the value created (£1,517.95) was categorised as monetarily returnable, whereas the remaining value (£3,260.40) was purely illustrative social value, for example improved mental well-being. Originality/value This unique pilot study demonstrates the health impacts and wider social value of providing a self-sampling sexual health service to prisoners within an open prison setting. By innovatively testing the feasibility of using a Health Impact Assessment process alongside Social Return on Investment analyses, this paper has outlined how the frameworks can be used in synergy to illustrate not just direct return on investment but also the social value of providing such a service.