Background: Social workers have previously been identified as being at risk of experiencing fatigue, stress and burnout. Social work is strongly client-based, with workers being involved in complex social situations. As such, they can experience many of the conflicts that are evident in human service work. In addition, the last decade has seen a transformation in the nature and practice of social work, as a result of administrative, societal, and political change. A number of writers have commented that much of what is known about stress and burnout among social workers is anecdotal and there is a lack of systematic research findings on this subject. Fatigue is generally defined as a sense of persistent tiredness or exhaustion that is often distressing to the individual. It is a common subjective complaint among Formal caregivers. Accordingly, the etiology of fatigue is believed to be multifactorial. Fatigue is often described by those who experience it in terms of physical, mental, and emotional tiredness. These sensations may be sufficiently consistent as to be characterized as unidimensional or, conversely, as sufficiently distinct in their expression as to be characterized as different dimensions of fatigue. This multidimensional characterization of fatigue is evidenced by the large number and variety of multidimensional fatigue measures currently available. The psychological consequences of providing social support and care to traumatized individuals have been under study for over 2 decades; however, few studies have focused on Formal caregivers (i. e., therapists, child protection workers, nurses, social workers, etc. ) and their emotional response to dealing with traumatized clients. Studies have shown that providing such care can be both highly rewarding and highly stressful. Individuals working in the care-giving professions, though, may have occupational environments and caregiving demands that increase the likelihood of adverse psychological outcomes Theoretically, individuals working in the caring professions often attempt to alter the behaviors and emotions of their clients by providing emotional support (e. g., empathy), strategies for coping with emotions, or better cognitive management skills. Within the context of Formal caregiving, providing therapy to clients who have survived a traumatic event can be particularly stressful. Many researchers have indicated that therapists who work with traumatized clients often show signs of psychological distress as a result of these interactions. The adverse impact of working with clients who have a history of psychological trauma (e. g., sexual and physical abuse, military combat, or community disaster) has been described under a variety of terms: vicarious traumatization, secondary traumatic stress, and fatigue. Method: The present study is a cross-sectional descriptive study that examines multidimensional fatigue in Iranian social workers. This study was conducted from July to November, 2019. The statistical population of the study consisted of all those working in the field of social work in Iranian governmental and non-governmental organizations who were employed at the time of the study. Sampling was done by available method and snowball. A total of 334 people participated in the study. In the present study, the MFI standard questionnaire was used to measure fatigue, which is recognized as one of the most effective and most complete multidimensional fatigue measuring tools. A review of the literature and a history of applying the MFI questionnaire indicate that numerous studies have been carried out worldwide using the above-mentioned questionnaire. This questionnaire provides a deeper and more accurate understanding of a person's fatigue by assessing the extent of general fatigue, physical fatigue, reduced activity, reduced arousal, and mental fatigue. In fact, the MFI measures fatigue in the way that a person feels. General physical exhaustion is related to one's overall day-to-day functions, physical exhaustion is related to physical sensation that is directly related to exhaustion, mental exhaustion is associated with reduced cognitive skills, reduced daily activity, and reduced activity and routine activity. Reduction of motivation refers to a decrease or lack of motivation to start any activity. This questionnaire is applicable to the population of patients and healthy people and consists of 20 items rated on a 5-point Likert scale (from 1 = yes completely right to 5 = completely wrong). Ultimately, higher scores indicate a higher degree of fatigue. It is noteworthy that four questions were considered for each dimension and simultaneously positive and negative orientations were used to reduce the likelihood of bias. The total score for each dimension is 4– 20 and the total fatigue score which is achieved by summing the scores of the areas is between 20 – 100. This questionnaire was first presented by Smiths in 1996, and its validity and reliability in different groups of cognitive populations, such as patients with cancer who were undergoing radiotherapy, patients with concomitant fatigue syndrome, first-year psychology and medical students, soldiers, and third-year medical students were evaluated. Alpha-Cronbach's coefficient was higher than 80% for general, physical and mental fatigue and above 65% for reduced activity and excitement. Cronbach's alpha coefficient for this study was 69%. Demographic characteristics of the sample members including age, education, marital status, work experience, place of work, etc. were collected through a separate questionnaire and a sample questionnaire along with the main questionnaire. The questionnaire was prepared electronically and sent to social workers working in different fields via SMS, email, questionnaire link sharing in social worker social media groups and channels. Data was analyzed by SPSS version 22 using descriptive statistics, Mann-Whitney and Kruskal-Wallis tests. Results: The age of participants was 21 to 62 years with a mean and standard deviation of 38. 91± 23. 82. 84 (25. 1%) participants were male and 250 (74. 9%) were female. The mean and standard deviation of the fatigue score was 62. 72± 4. 9. Mental fatigue and reduced motivation with a mean of 12. 8 were the highest among the dimensions of fatigue. 66. 8% of participants reported too much fatigue. 32. 9% had moderate fatigue and only 0. 3% had no fatigue. The results of mean comparison showed that the mean score of fatigue of social workers in social services area (welfare organization, charity associations and hospitals) was higher than other areas. Age group 56-62 reported higher mean fatigue than other age groups. Social workers with more than 30 years of experience also reported greater job fatigue than others. The results of mean comparisons showed that the mean of fatigue dimensions was different in the different domains (Chi-Square = 6. 806 sig = 0. 047), in the different age groups (Chi-Square = 1. 715 sig=0. 034) and in individuals with different work experience (Chi-Square= 0. 861 sig=0. 035). Discussion: Due to the nature of the social work profession, employment in different workplaces creates different levels of fatigue for social workers. . Therefore, the fatigue caused by employment in this profession is inevitable, and training self-care practices and the ability to change and rotate in different areas of work for social workers can reduce the effects of job fatigue. Making sense of a career and reviewing the reasons for being a social worker are some of the things that can reduce job fatigue. Developing a personal philosophy that guides the thinking and practice of social work will also be effective.