The present study investigated the relationship between personality traits and psychological capital and academic adjustment. Methods: This was a cross-sectional research study. The study population comprised all male and female students at the University of Kashan in February-March 2018. A total of 360 (190 females and 170 males) students were selected by cluster sampling method. The Adjustment Inventory for College Students (AICS), HEXACO Personality Inventory, and Luthans Psychological Capital Questionnaire (PCQ) were used to collect data. To analyze the obtained data, a regression analysis was run by SPSS. Results: The analysis suggested a significant relationship between academic adjustment and honesty-humility (r=-0.19, P<0.01), emotionality (r=0.14, P<0.01), extraversion (r=-0.14, P<0.01), and conscientiousness (r=-0.32, P<0.01). Besides, a significant correlation was observed between academic adjustment and psychological capital (r=-0.17, P<0.01). The regression analysis results revealed that conscientiousness, emotionality, and honesty-humility predicted 13% of the variance in academic adjustment. Moreover, regression analysis results indicated that hopefulness predicted 3% of the variance in academic adjustment. Conclusion: The study results indicated a relationship between personality traits and psychological capital and academic adjustment. Furthermore, educational-counseling interventions oriented on personality and psychological capital could help promote student's academic adjustment.