This study investigates individual and group cognitive-behavioral interventions in decreasing psychological symptoms and enhancing the psychological status of Iranian prison inmates. A random sample of 180 males is placed in three equal groups: an individual cognitive-behavioral therapy (CBT) group, an individual and group CBT group, and a control group. General Health Questionnaire, Symptom Checklist-90- Revised, and diagnostic interviews based on the Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.) are used before and after intervention. MANOVA indicates that both methods improve the psychological status of the inmates and reduce their symptoms, but the combined treatment is more efficient than the individual therapy. In a 1-year follow-up after inmate release, recidivism in the individual and combined therapy groups is zero. The return rate of participants in the control group is 15%. Results of the study demonstrate that both individual and group CBT are effective in reducing psychological symptoms. However, the impact of combined therapy is stronger than individual CBT.