The aim of the present study is to investigate the relationship between defense mechanism styles and the quality of couples' relationships with the mediating role of marital conflict resolution styles. 244 couples were selected from the couples of Jam City by available sampling method. Andrews's Defensive Style Questionnaire and Rahim's Organizational Conflict Inventory and Couples Relationship Quality Scale were filled out by participants. The research data were analyzed using path analysis and AMOSE software. The results of the research showed that immature and mature styles among defensive styles and, integrating, avoiding, compromising and obliging styles‌‌ among conflict resolution styles have significant relationships with the quality of couples' relationships. In examining the indirect relationships of the research, it was also found that the integrating and obliging conflict resolution styles mediate the relationship between immature defensive style and the quality of the couple's relationship, also the integrating and compromising conflict resolution styles mediate the relationship between mature defensive style and quality of the couple's relationship. Therefore, according to the findings of the research, it can be concluded that examining defensive styles and conflict resolution styles can be useful in predicting and improving the quality of couples' relationships.