Abstarct: The present study investigates the effect of employer brand on organizational citizenship behavior by mediating the employment of employees of sport and youth offices in Semnan province. The research method was descxriptive and correlational. The statistical population of this study consisted of all employees of sport and youth departments of Semnan province (n = 120). A total of 120 questionnaires were distributed among all staff, 91 of which were completed and analyzed as samples. The data were collected using the Client Brand Questionnaire (Burton et al., (2005), Organizational Citizenship Behavior (Organ & Kanusky, (2005) and Job Involvement Questionnaire (Ladahel & Connor, 1965). Data were analyzed using SPSS 16 and SMART PLS 3 software. Findings indicated that employer brand had a positive and significant effect on organizational citizenship behavior; on the other hand, job involvement had a positive and significant effect on organizational citizenship behavior. The results also showed that job involvement variable can mediate the relationship between employer brand ambiguity and organizational citizenship behavior. According to the findings of the present study, managers can encourage employees to increase their organizational citizenship behavior as well as increase the level of involvement of their employees by strengthening the employer brand by adopting measures to improve the quality of the work environment and increasing the amount of cash and non-cash benefits and benefits.