Abstarct: The aim of the present study was to investigate the effect of work-family conflict on the job performance of physical education teachers in Semnan province with the role of mediator and moderator of job stress. The research method was correlational. The statistical population included all physical education teachers in Semnan province, 300 people. According to Klein's theory and the available sampling method, 159 people were selected as a statistical sample. The House and Reserve Job Stress Questionnaire (1972), the Family-Work and Work-Family Conflict of Net-Meyer et al. (1996), and Boyle et al. (2019) were used to collect data. Cronbach's alpha coefficient was used to measure the validity of the questionnaire from the perspective of teachers and to measure the reliability of the questionnaires. Structural equations with a variance-baxsed approach were used to examine the research hypotheses. SPSS 24 and Smart-PLS 4.2.8 software were used to analyze the data. The results of the study showed that work-family conflict and family-work conflict have a negative and significant effect on job performance, and there is also a negative and significant relationship between job stress and job performance. The relationship between family-work conflict and job stress is also a negative and significant relationship. Finally, in the relationship between work-family conflict and job performance, the job stress variable has a moderating (negative) role, and also in the relationship between family-work conflict and job performance, the job stress variable has a mediating (negative) role. According to the results of the study, it is suggested that appropriate training courses such as work-family balance, training in skills such as time management, stress management, etc. be planned.