The aim of this study was to investigate the effect of transformational environmental leadership, organizational environment policy and environmental education on the behavior of organizational citizenship towards the environment with the mediating role of environmental beliefs and the moderating role of organizational environmental support. The type of research is descriptive survey and the statistical population of this research is all managers, deputies and senior experts of OIEC Petroleum Engineering and Construction Company who have sufficient knowledge and competence to answer the questions of the questionnaire and their number is 700 people. To determine the minimum required sample size, Cochran's formula was used for a limited population. For this purpose, using the available sampling method, questionnaires were distributed among 248 members of the statistical sample. The data collection tool of the present study is a questionnaire that the reliability of the present research questionnaire was measured by calculating the Cronbach's alpha coefficient, which was higher than 0.7 for all research variables.Structural equation modeling using AMOS software has also been used to analyze the data. The results of the present study confirmed the effect of transformational environmental leadership and environmental education on environmental beliefs. The effect of transformational environmental leadership and organizational environment policy on organizational citizenship behavior was also confirmed. The mediating role of environmental beliefs in the relationship between transformational leadership and environmental education with organizational citizenship behavior was also confirmed.