Aim: The present study purpose was to determine the mediating role of psychological capital in the relationship between personality features neuroticism, openness, extroversion, agreeableness and conscientiousness with marital adjustment in university students. Method: The research method was descriptive-correlational and the statistical population included all married female students of Islamic Azad University, Karaj Branch, in the first semester of 2017-2018 with the quantity of 33000 people, among them 300 subjects Based on Kline's (2011) proposal from faculty of psychology classes were selected through sampling. The study tools included Dyadic Adjustment Scale by Spanier (1976), NEO-Five Factor Inventory by McCrae & Costa 1985 and Psychological Capital Questionnaire by Luthans, Avolio, Avey & Norman (2007). After exclusion of 3 distortion questionnaires and removal of 1 outlier subject, the data of were analyzed using Structural Equation Modeling Method. Results: The results of this study showed that the indirect path coefficient between openness and marital adjustment (β = 0. 066, P= 0. 016, ), indirect path coefficient between extraversion and marital adjustment (β = 0. 083, P= 0. 012), and indirect path coefficient between neuroticism and marital adjustment (β =-0. 117, P= 0. 001) were significant. Conclusion: Personality traits, as the preconditions that individuals enter into marital relationships, are likely to affect individuals' equity including optimism, self-efficacy, hope, and resilience in dealing with marital problems, may be leading to reduce or increase marital adjustment. Therefore, it is suggested that workshops aimed at promoting the psychological capital for married female students in universities should be held.