This study examines the changes in clinical risk factors among individuals treated in Dutch Penitentiary Psychiatric Centers (PPCs). Using data from 874 patients with diverse psychiatric disorders, clinical risk factors were assessed at admission and discharge. Slight but significant improvements were observed in most risk factors, particularly psychotic symptoms, over an average stay of approximately 6 months. Patients with psychotic or substance use disorders showed the most improvement, while those with mood, personality, or developmental disorders showed minimal change. The study highlights the positive impact of PPCs’ structured, secure environment and specialized treatment, especially for psychotic disorders. It also underscores the complexity of treating patients with high rates of comorbidity. The findings suggest that the duration of stay does not significantly predict the improvement in most clinical risk factors. Future research should explore specific diagnostic clusters and their impact on treatment outcomes in PPCs.