The interdependence between human and environment manifest the necessity of investigating human impact on environmental degradation or on environmental protection. The present research aims to develop a causal model of effective factors on environmentally friendly behavior among high school students in Shiraz. This is applied research with a descriptive method. Using an adapted questionnaire, we examined the effect of the variables, including environmental concern, attitude, knowledge, subjective norms, responsibility perception, and dependence on nature, on environmentally friendly behavior. The correlation coefficient was used to examine the effect of different variables on each other, and the path analysis method was used to analyze the relationships between the variables of the research. The research community is the first-grade high school students in Shiraz in the academic year 2018-2019. 360 individuals from among 58863 numbers of students were selected as study samples through Krejcie and Morgan table. The research results providing a good of fit of the proposed model indicate that environmental concern, attitude, and knowledge have a significant direct effect on environmentally friendly behaviors. Moreover, subjective norms, responsibility, and dependence on nature have a significant indirect effect on environmentally friendly behavior via mediator variables (environmental concern, attitude, and knowledge). Furthermore, the responsibility perception among endogenous variables has the greatest effect (0.76) and the environmental knowledge among exogenous variables has the greatest effect (0.40). Since environmental responsibility perception has the greatest effect on the environmental attitude and knowledge variables, and via these variables, it has an indirect effect on the environmentally friendly behavior, it is essential to take necessary measures to increase students’ responsibility for environ.