Introduction:It is important to pay attention to personality traits and psychological capitals in nurses' job stress. The purpose of the research was the role of personality traits in the psychological capital of nurses with the mediating role of o job stress. methods:The descriptive research method was correlation type. The statistical population was nurses of Tehran University of Medical Sciences. The sample size of 220 people was selected by voluntary sampling. The tools of data collection were questionnaires of personality traits, psychological capital and job stress. Data analysis was done using Pearson's correlation test and structural equation model with SPSS and AMOS software version 24. Results:Pearson's correlation test showed that there is a significant relationship between personality traits, psychological capital and job stress. Also, the results of the Sobel test showed that job stress plays a mediating role between personality traits and psychological capital (P≥0.05). Conclusion:Nurses who have favorable personality traits and psychological capital are expected to have low job stress.