Abstract We present a study about an ethics support instrument, Moral Case Deliberation (MCD), which is used to support and further professionalize Dutch prison staff. MCD can facilitate prison staff in dealing with moral dilemmas from practice. We present an embedded mixed-methods study on the experienced outcomes of 16 teams participating in both single and in series of MCD sessions. Prison staff and MCD facilitators completed evaluation forms ( n = 871 by staff, and n = 122 by facilitators) after participating in a single MCD session ( n = 131). Staff filled out another evaluation form ( n = 149) after participating in a series of 10 MCD sessions. Our multilevel quantitative analyses show overall positive outcomes, with significant differences between professional disciplines. Prison staff, e.g., reported a better understanding of the discussed moral dilemma and the related perspectives of colleagues. The qualitative thematic content analysis of the experienced outcomes of single MCD sessions resulted in 8 outcome categories, e.g., improved moral awareness, awareness of responsibilities and limitations in decision-making, and feeling empowered to address issues. The experienced outcomes of MCD provide some insights in the process of fostering moral learning of prison staff; staff gained moral awareness, and improved their perspective-taking and the ability to better control their frustrations and emotions. Further research should focus on studying the impact of MCD on moral decision-making in the day-to-day practice of prison staff and on what the organization can learn from the MCD sessions.