This chapter builds upon Chap. 10 by posing questions about the potential of prisons as a setting for health and wellbeing improvement. It gives an overview of health and wellbeing issues in prisons, before describing a whole-system (or “whole prison”) programme being facilitated in a number of prisons across England. Findings from a mixed-method evaluation using quantitative scales (the Warwick-Edinburgh Mental Wellbeing Scale and the Connectedness to Nature Scale), and qualitative data in the form of thematically analysed verbatim quotes from people in prison and staff involved with the programme, are presented using a Model of Health Determinants framework. The chapter then presents an individual case study “pen portrait” of participation in the Greener on the Outside for Prisons programme, to demonstrate the health and wellbeing benefits of nature connection in prison settings. Finally, the potential of therapeutic horticulture for prisons and, by extension, wider society in the future is discussed.