Positive effects of Positive Behavior Intervention and Supports (PBIS) frameworks have been reported in juvenile justice facilities but have not yet been extended to adult prisons. As part of initial PBIS development in a large prison in the United Kingdom, this study utilized focus groups to investigate the valued outcomes considered most important to prison officers and prisoners. We found that although prisoners and staff largely shared the same values, there were meaningful differences in their relative priorities, reflecting the disparate roles that each play in the functioning of the prison. Focus groups also revealed possible contextual barriers to PBIS implementation in this setting. We conclude that input from both parties is essential in designing values-based support strategies that are aligned across key stakeholders. We discuss how focus groups might inform PBIS intervention planning and how our findings point to specific research gaps in applying PBIS in adult prisons.