Background and Aim: The tendency to understand the factors and consequences of work fatigue has increased in recent decades because work fatigue can affect health, safety attitudes, and personal and work performance. The effects of work fatigue subsequently affect a number of individual (physical, psychological, behavioral, and inability to protest) and organizational elements (job attitudes, job attendance, poor performance, and work trauma). Therefore, the present study aimed to investigating the psychometric properties persian version of the work fatigue inventory. Methods: In this study, 360 employees of Ahvaz Fire Department were selected by random staging. The research method was descriptive tool validation. Participants completed questionnaires on job fatigue, role ambiguity, role conflict, job satisfaction, mental health and turnover. The internal consistency of the questionnaires was assessed by Cronbach's alpha method and correlation coefficient of the whole test. Convergent validity, empirical validity, and incremental validity were used to assess the validity of the Fatigue Scale. Results: Exploratory factor analysis using the principal components method and the varimax cycle, showed that physical, psychological, and emotional exhaustion consisted of a factor called work exhaustion. Confirmatory factor analysis showed that, except for one material, the scale significantly loaded on one factor. The results of convergent validity showed that the scale of work fatigue was positively correlated with the ambiguity and role conflict and intention to leave jobs and was related to job satisfaction scales. The results of empirical validity showed that work fatigue scale is related to job satisfaction. The results of incremental validity using hierarchical regression analysis showed that work fatigue scale predicted more than the effect of work fatigue factor and the other four measures of job satisfaction. Conclusion: Overall, the findings of the study showed that the scale of work fatigue is acceptable and consistent with Western research. As a result, it can be used to measure this structure in Iranian staff.