Personality disorders can lead to difficult social or occupational functional processes rooted in chronic maladaptive thoughts, feelings, and behaviors. This study aimed to investigate factors of personality disorder in prisoners from the central prison of Sanandaj, Iran. We conducted a cross-sectional study, which included all prisoners in the central prison of Sanandaj, Iran. The study sample includes 343 prisoners, of which 329 were male, and 14 were female, selected by randomized multistage sampling method. Participants filled in Millon’s multi-axis clinical questionnaire. The data were analyzed using Chi-square, multiple logistic regression, and bootstrap analysis. There were 183 participants without personality disorders (53.4%) and 99 participants (28.9%) with cluster B personality disorders (narcissistic, histrionic, anti-social, and borderline). Male gender (OR=0.07) and elementary education level (OR=0.18) have a significant relationship with cluster A personality disorders (paranoid, schizoid, schizotypal). Cluster B has a significant relationship only with the elementary education level (OR=0.27). Cluster C (avoidant, dependent, obsessive-compulsive personality disorder) has a significant relationship with male gender (OR=0.20), elementary education level (OR=0.30), unemployment (OR=2.64), theft crime types (OR=0.38) and disputes and assaults (OR=0.18). Based on these results, psychological and psychiatric interventions in prisoners are suggested.