Background: Prisoners are a vulnerable group within societies, and also threaten society due to their dangerous behavior. The objective of the present study was to evaluate the relationship between prisoners’ personality disorders and their crime and substance use.Methods: This was a descriptive-correlational study. The statistical population consisted of all prisoners of Kerman, Iran. Through stratified random sampling, 228 prisoners (114 women and 114 men) were selected as the study subjects. Data were collected through clinical interviews by a psychiatrist [structured interviews based on the Diagnostic and Statistical Manual of Mental Disorders-4th Edition (DSM-IV)], a social worker, and a physician and using a demographic characteristics questionnaire and the Millon Clinical Multiaxial Inventory-2th Edition (MCMI-II) (the 175-item Persian version). Data were analyzed using frequency, percentage, and Fisher's z-distribution in SPSS software.Findings: The results showed that 87.3% of women and 83.3% of men had a personality disorder at the time of committing the crime. Moreover, 46.5% of the target population had developed substance dependence at the time of committing the crime. The highest percentage of substance abuse in both women and men was related to opium, especially in the age group of 18-28 years. The highest rates of mental disorders were related to major depressive disorder (MDD), dependent personality disorder (DPD), borderline personality disorder (BPD), and antisocial personality disorder (ASPD), respectively. In these personality disorders, opium, methamphetamine, heroin, and alcohol, respectively, had the highest rates of use. The results of Fisher's z-distribution illustrated a significant relationship between personality disorders and type of crime committed and substance used. The total rate of substance abuse was lower in sexual offenses and fraud, but was the highest in theft and drug trafficking.Conclusion: The presence of personality disorders in the target population is indicative of the need for judicial officials’ attention to this effective factor in crime and the use of mental health services and treatment instead of the penalty of deprivation of liberty.