There has been a recent surge in academic research into military veterans in the criminal justice system but little of this has focused on UK military veterans in prison. This study contributes towards filling this gap in the research literature. The study used semi-structured qualitative interviews with 35 serving ex-military prisoners in six prisons across England to explore the experience of imprisonment amongst UK veterans in prison. Using thematic analysis, it maps out participants’ life pathways, from childhood through military service and into prison. In doing so, it reveals the strong, persistent military identity that veteran prisoners held and the military mind-set that they employed in managing their lives in prison. It identifies clear similarities between the military and the prison, including the physical environment and their organisational structures and cultures, supporting Goffman’s (1961) conception of the total institution, while also highlighting differences between the fragmented, individualistic social world of the prison and the collective and cohesive social world of the military. The study found that veterans employed their military mind-set and drew on their experiences of encountering physical and mental hardships in their previous military service to cope with the pains of imprisonment. It discovered a preference for highly-structured and disciplined prison regimes, with some veterans exhibiting degrees of institutionalisation. It examines how veterans navigated the social world of the prison, struggling to relate to most other prisoners while often bonding with other fellow veterans. It also explores veterans’ attitudes towards authority, reflected in acceptance of their prison sentences, compliance with the institution’s regime and a belief in the legitimacy of the nation state. Finally, it reveals veteran prisoners’ concerns around their safety in prison and their positive perceptions of and relationships with prison staff, especially those who themselves were military veterans. Implications for policy-makers and practitioners managing military veterans in the criminal justice system are discussed, as well as proposed future areas of research.