Background and aims: Job burnout is a prolonged response to chronic emotional and interpersonal stressors on the job. Energy depletion (exhaustion), depersonalization and reduced professional efficacy are considered to be characteristic components of burnout. Emotional exhaustion is the central dimension of burnout and refers to feelings of being emotionally depleted due to over-extension. Cynicism or depersonalization, is the interpersonal dimension of burnout that develops as a protection against feelings of exhaustion. When the exhaustion becomes too overwhelming for the individual, he or she detaches from the work and becomes cynical and disconnected from clients and co-workers. Reduced personal accomplishment refers to the feeling of loss of efficiency and productivity at work (also termed loss of professional efficacy). Maslach and Goldberg (1998) propose that the interrelationship between emotional exhaustion and depersonalization is a causal one whereby feelings of emotional exhaustion lead to depersonalization. The third dimension, reduced personal accomplishment, is posited to develop separately. A considerable body of research has examined the negative effects of job burnout on employees and their organizations. The consequences, or costs of burnout are seen most consistently in various forms of job withdrawal (decreased commitment, job dissatisfaction, turnover, and absenteeism), with the implication of a deterioration in the quality of care or service provided to clients or patients. As such, it has been recognized as a major problem worldwide. Studies emphasize the importance of the identification of predictive factors of this phenomenon for the purposes of prevention and intervention. There are a number of studies detailing factors related to job burnout. These factors can be categorized into professional traits, social organization traits, and personal traits. Maslach (1988) found that personality traits and dimensions could justify burnout. He concludes that job burnout is associated with neuroticism and psychological profile of work-related fatigue. In addition to personality traits, basic psychological needs satisfaction is essential for the growth and wellbeing of employees in the workplace. Social determinant theory emphasizes the needs for autonomy, competence and relatedness. Autonomy refers to the experience of volition and self-endorsement of one’ s behavior, competence refers to the desire to master one’ s environment and attain valued outcomes within it and the need for belongingness or elatedness is defined as the human striving for close and intimate relationships and the desire to achieve a sense of communion and belongingness. Several empirical studies have found basic need satisfaction to associate positively with individual’ s optimal functioning in terms of well-being, attitudes and behavior, employees’ well-being, job satisfaction, intrinsic and autonomous work motivation, time spent voluntarily at work, performance evaluations, vigour and dedication, whereas it has associated negatively with emotional exhaustion. Psychological flexibility, a key construct of Acceptance and Commitment Therapy (ACT), has recently been found to be an important determinant of mental health and behavioral effectiveness in the workplace. It refers to people’ s ability to focus on their current situation and based upon the opportunities afforded by that situation, take appropriate action towards achieving their goals and values, even in the presence of challenging or unwanted psychological events (e. g., thoughts, feelings, physiological sensations, images, and memories). Psychological flexibility has been found to enhance employees’ ability to handle work strain and to reduce employee burnout. In line with these findings and the mentioned arguments, this research was conducted with the aim of studying the relationship between personality traits, workrelated basic psychological needs satisfaction, work-related psychological flexibility with job burnout. Methods: This is a practical descriptive-correlation research. Its statistical population consisted of all staff who worked in Islamic Azad University branch of NajafAbad, from whom 200 employees (144 men and 56 women) were selected randomly by cluster sampling method. Data were collected using Neo Personality Scale (NEO-FFI-R) (Costa and MacCrae, 1991); Work-related Basic Need Satisfaction Scale (Van den Broeck, 2010); Work-related Acceptance and Action Quesionnaire (WAAQ) (Bond et. al, 2013) and Job Burnout scale (Maslach & Jackson, 1981). The 60-item NEO Five-Factor Inventory (NEO-FFI) was developed to provide a concise measure of the five basic personality factors (neuroticism, extraversion, agreeableness, conscientiousness and openness to experience). For each scale, 12 items were selected from the pool of 180 NEO Personality Inventory (NEO-PI) items. The items are rated on a 5-point Likert-type scale ranging from 1 (completely agree) to 5 (completely disagree). Higher scores in every personality factor indicate greater levels of that personality factor. Work-related Acceptance and Action Questionnaire (WAAQ) is a 7-item scale that measures psychological flexibility in relation to the workplace. The items reflect the extent to which people can take goal-directed action in the presence of difficult internal experiences (e. g., “ I am able to work effectively in spite of any personal worries that I have, ” “ I can still work very effectively, even if I am nervous about something, ” “ I can work effectively, even when I doubt myself” ). The items are rated on a 7-point Likert-type scale ranging from 1 (never true) to 7 (always true). Higher scores indicate greater levels of work-related psychological flexibility. Work-Related Basic Need Satisfaction Scale (W-BNS) was developed by Van den Broeck et al. (2013). The scale contains 16 items, and is a 5-point Likert-type (from 1 = completely disagree to 5 = completely agree). W-BNS has three sub-dimensions: competency need, relatedness need and autonomy need. The “ competency need” sub-dimension implies individiual’ s feeling himself/ herself competent at work (Sample Item: I feel competent in my job). The “ relatedness need” sub-dimension implies individiual’ s need to build relationships with others and to avoid loneliness and isolation at work (Sample Item: At work I feel part of a group). The “ autonomy need” subdimension is related to individual’ s initiating activities, making decisions and choices independently at work (Sample Item: I feel free to do my job the way I think it could best be done). The Maslach burnout index (MBI) is designed to assess the three components of the burnout syndrome: emotional exhaustion, depersonalization, and reduced personal accomplishment. There are 22 items, which are divided into three subscales. The items are written in the form of statements about personal feelings or attitudes (e. g; “ I feel burned out from my work” , “ I don’ t really care what happens to some recipients” ). The items are answered in terms of the frequency with which the respondent experiences these feelings, on a 7-point scale, ranging from “ never having those feelings” (0) to “ having those feelings every day” (6). The nine items in the emotional exhaustion subscales assess feelings of being emotionally overextended and exhausted by one’ s work. The five items in the depersonalization subscale measure an unfeeling and impersonal response toward recipients of one’ s service, care, treatment, or instruction. For both the emotional exhaustion and depersonalization subscales, higher mean scores correspond to higher degrees of experienced burnout. The eight items in the personal accomplishment subscale assess feelings of competence and successful achievement in one’ s work with people. In contrast, to the other two subscales, lower mean scores on this subscale correspond to higher degrees of experienced burnout. Data were analyzed using descriptive statistics (mean and standard deviation), Pearson correlation coefficient and multiple regression analysis (stepwise method) with SPSS software (v. 21). Results: Mean and (standard deviation) scores for research variables were: neuroticism = 32. 20 (6. 78), extraversion = 42. 38 (5. 74), agreeableness = 44. 11 (5. 10), conscientiousness = 48. 36 (5. 64), openness to experience = 35. 95 (4. 25), autonomy = 17. 65 (3. 69), competence = 15. 97 (2. 43), relatedness = 21. 43 (4. 16), psychological flexibility = 33. 74 (6. 96), emotional exhaustion = 14. 46 (11. 93), depersonalization = 3. 95 (4. 95), reduced personal achievement = 10. 8 (9. 11) and job burnout = 33. 22 (18. 15). Pearson correlation analysis results indicated that there is a negative relationship between autonomy (r=-0. 49, p<0. 01), competence (r=-0. 36, p<0. 01) and relatedness (r=-0. 46, p<0. 01) with job burnout. Also there is a significant negative relationship between work-related psychological flexibility with job burnout (r=-0. 38, p<0. 01), emotional exhaustion (r=-0. 26, p<0. 01), depersonalization (r=-0. 28, p<0. 01), and decreased personal achievement (r=-0. 26, p<0. 01). Among personality traits, extraversion (r=-0. 51, p<0. 01), conscientiousness (r=-0. 35, p<0. 01) and agreeableness (r=-0. 29, p<0. 01) were negatively and significantly related to job burnout. There was a positive and significant relationship between neuroticism and job burnout (r=0. 43, p<0. 01). Moreover, stepwise regression analysis results revealed that extraversion, autonomy, conscientiousness, relatedness and psychological flexibility with negative relationship have a significant role in predicting staff job burnout (p<0. 05). In total 45% of job burnout variance was explained by these variables. Emotional exhaustion was predictable respectively via autonomy and relatedness. These variables can predict 44% of emotional exhaustion variance significantly (p<0. 001). Results also showed that extraversion and conscientiousness can predict 25% of decreased personal achievement (p<0. 001). Finally, conscientiousness and psychological flexibility can predict 12. 1% of depersonalization variance significantly (p<0. 001). Conclusion: According to the results of the current study, it can be concluded that Psychological flexibility, basic psychological needs satisfaction and personality traits, particularly extraversion have a key role in job burnout development, and thus should regularly be considered in burnout research and therapy. Based on the results of this study, it is suggested that managers choose staff with high level of extraversion, agreeableness, conscientiousness and flexibility and low level of neuroticism. They also should change the working environment conditions so that the basic needs of employees be met.