Abstarct: The aim of this study was to investigate the effect of service quality on word of mouth advertising of customers of fitness clubs with a mediating role of satisfaction. The method of this research was descxriptive information collection and correlation schemes. The statistical population of this study consisted of customers of bodybuilding clubs in Kashan, whose number was unlimited. To estimate the sample size, G-Power sample size software was used and 123 people were selected as the research sample. Data were collected using Liu (2008) Quality of Service Questionnaire, Darzi and Bahat Customer Satisfaction Questionnaire (2018) and Kim (2008) word of mouth and using structural equation modeling and partial and soft least squares approach. PLS software were analyzed. The results showed that the quality of services has an effect on word of mouth and customer satisfaction of bodybuilding clubs in Kashan. Satisfaction affects the word of mouth of customers of Kashan bodybuilding clubs. The results also showed that satisfaction does not play a mediating role in the relationship between service quality and word of mouth of customers of Kashan fitness clubs. Therefore, the quality of bodybuilding club services increases customer satisfaction and word of mouth. Customer satisfaction also increases word of mouth