Abstarct: The aim of the current research was to explain the effect of leisure sports mania on pro-environmental behavior with the role of internal motivation. The present study was a survey descxriptive research method. The statistical population of this research was made up of people using Safeh Mountain Park in Isfahan. Jpower sample size estimation software was used to estimate the sample size and 210 people were selected as the research sample. The sampling method in this research was non-probability available. Data were collected using questionnaires of leisure mania, pro-environmental behavior and intrinsic motivation of Lee and Jeong (2018) and using structural equation modeling and partial least squares approach and PLS and SP software. SS were analyzed. The results of the research showed that leisure time sports mania has a positive and significant effect on the inner motivation of people using Sefe mountain park, and inner motivation has a positive and significant effect on people's environmental protection behavior, and leisure time exercise mania has an effect on people's environment protection behavior. It is positive and meaningful. Also, the results showed that intrinsic motivation plays a mediating role in the relationship between leisure sports mania and pro-environmental behavior of people using Sefe Mountain Park. Therefore, it should be noted that the more the interest in spending leisure time in the environment increases, the more the number of people who support the environment will increase and fight against those who destroy the environment, and to create interest in spending leisure time Regarding the environment, it is necessary to inform people about its benefits through information brochures, clips, power, etc.