The purpose of this research is to determine the predictive role of the dark Triad of personality traits and couples' communication patterns in marriage instability. This study is of correlational type and the statistical population was couples living in Tehran and Karaj cities. 246 people were selected by available sampling method, and the Marital Instability Index (MII), short form of the dark triad scale (SD3) and communication patterns questionnaire (CPQ) were administered. The data were analyzed using the stepwise multiple regression method. The findings showed that the variable of marriage instability has a negative and significant relationship with narcissistic personality traits and a positive and significant relationship with antisocial personality traits and has no significant relationship between marital instability and Machiavellian personality traits. Similarly, the variable of marriage instability shows a negative and significant relationship with the variable of mutual constructive communication and with other variables of withdrawal/demand, demanding man/withdrawn woman, demanding woman/withdrawn man and mutual avoidance, and a positive and significant relationship with other variables of communication patterns. Also, the three variables of constructive communication, mutual avoidance and demanding woman/withdrawn man predict the instability of marriage. In addition, there is a negative and significant relationship between the duration of marriage and the instability of marriage. From this research, it can be concluded that considering the role of communication patterns in marriage instability, marriage instability can be reduced by teaching them to couples.