In this study, I try to examine the effect of environmental sustainability on CEO RISK TAKING. Prior research, however, has struggled to establish this relation empirically; moreover, some evidence points to the possibility that the CEO RISK appetite is lower for firms with sustainable environment. The opportunistic approach of managers leads to decisions about personal interests and imposing costs on shareholders by decreasing RISK TAKING. In order to investigate the issue, data on companies listed in Tehran Stock Exchange for the period 2008-2018 were extracted and a panel regression model was used to test the research hypotheses. Consistent with expected relation between CEO RISK TAKING and the environmental sustainability, It decreases with respect to CEO opportunistic approach. Managers may benefit from increased fluctuations in RISK orientation, but are more sensitive than shareholders and have less restrictive choice that avoids higher RISK.