Environmental Impact Assessment is a tool in ensuring environmental protection. Projects which impact the environment significantly are assessed with the aim of predicting the consequences as well as identifying appropriate measures for minimizing the adverse effects the project may have on people and their property as well as the environment. The Environmental Assessment Act, 1992 while providing details as to environmental assessment, makes for the enforcement of the stipulations in the Act through an Agency. Formerly known as Federal Environmental Protection Agency (FEPA) (created under the repealed Federal Environmental Protection Agency (FEPA) Act), the National Environmental Standards, Enforcement Agency (NESREA) (created under the National Environmental Standards, Enforcement Agency (NESREA) Act), is the Agency charged with the responsibilities of enforcing all provisions of Environmental Impact Assessment Act, in Nigeria. This research work is on the challenges as faced by the regulator i.e. NESREA in enforcing the provisions of environmental impact assessment. The work defines environmental impact assessment as well as outlines the role and function of Environmental assessment. The work looks in brief the international provisions for environmental assessment as well as environmental impact assessment in Nigeria. NESREA as the regulator is ex-rayed as to the enforcement of Environmental Impact Assessment in Nigeria. The doctrinal research methodology was employed in writing this paper. The paper identifies several challenges faced by NESREA and makes recommendations as to capacity building, infrastructure, funding, increase sanctions and penalties amongst others.