Objectives: The growing increase in criminal acts in human societies has made criminologists study the sources and causes of criminal behavior. Method: This research was carried out as cross-sectional study on 136 male criminal inmates in Tehran prisons using SCL-90 -R. Findings: These people were in the age range of 30-37 with an average age of 33.6, about 87% of them had psychological disorders, among which aggression, anxiety, and somatization were the most abundant and OCD & phobia, the least (P<0.01). Conclusion: This investigation clearly shows that majority of the cases under study suffer from some of psychological disorders such as aggression, depression, paranoia etc. Although according to Islamic Criminal Law these psychological disorders do not result in a reduction in penalty responsibility, at the presence of mild psychological disorders, tendency to commit more severe crimes may increase