The importance of self-esteem in the development and maintenance of psychotic experiences has been shown in previous research. However, there has been little research into the role this plays in individuals with psychosis and forensic histories. The current study investigated the effectiveness of a standardized group programme for improving self-esteem in individuals with psychosis living in high security settings. Fifteen participants were included in the group programme and measures were taken to record changes in self-esteem and symptomatology. The results demonstrated significant improvements in self-esteem over the course of the group intervention, with some effects maintained at 3-month follow-up. Improvements in depressed mood were also found. The results demonstrated the effectiveness of a group intervention for self-esteem in individuals with psychosis. The findings of this study, alongside implications for further research, are discussed.