Adequate sustainability of environmental reporting reveals the extent of transparency and corporate efforts in protecting the environment. The study investigated the effect of corporate governance on environmental protection index of sustainability reporting in oil and gas companies quoted in Nigeria. The research design adopted was expostfacto. The population of the study is the entire 12 oil and gas companies listed in the Nigerian stock exchange market from which 8 companies were selected using judgmental sampling technique. The data analyzed were obtained from the financial statement of the selected companies for the period of 15 years ranging from 2006 to 2020. Environmental disclosure checklist in line with Global Reporting Initiatives was adopted to measure the proxies of environmental protection index of sustainability. Multiple regression was used in analyzing the data.it was revealed that corporate governance had significant effect on environmental protection, (AdjR2 = 0.123; Walt-test = 39.29; P-value = 0.000). Also, Firm size and firm leverage significantly moderated the effect of corporate governance on environmental protection, (AdjR2 = 0.216; F-Statistics = 34.58; P-value = 0.000). the study concluded that corporate governance significantly impact on environmental protection and also that firm size and firm leverage moderated the effect of corporate governance on environmental protection, it was recommended that the management should ensure strong commitments and adequate disclosure of all environmental protection policies, and set full compliance as priority; also that government should provide an enabling business operating environment which will enhance effective environmental sustainability reporting.