Seeking to disseminate cost-benefit analysis as part of a global agenda of reforms on regulatory policy, the Organization for Economic Cooperation and Development (“OECD”) has advocated this economic tool to all its member countries. A key partner of that international organization since 2007, Brazil officially sought in 2017 to be a permanent OECD member, which means accepting orientation from that organization on policy reforms, namely regulatory policy. This Article disagrees with OECD’s recommendation because traditional cost-benefit analysis has been technically flawed and politically biased towards a deregulatory agenda. The purpose of this Article, therefore, is to analyze the potential impacts of introducing cost-benefit analysis for environmental law and policy in Brazil. To achieve this goal, understanding the particular background and features of environmental law and policy in Brazil becomes essential. In this sense, this Article argues that cost-benefit analysis creates a particular risk to environmental law and policy in Brazil due to at least three factors: (a) it would reinforce the already strong presidential dominance over the regulatory agenda on environmental protection, undermining environmental agencies’ authority and scientific-based decisions; (b) it would imperil any possibility of improvement of the current levels of transparency, participation, and accountability on the decision-making processes for environmental laws and regulations; (c) it conceals a regulatory policy against new and existing laws and regulations on environmental protection.