This study is within the scope of Brazilian environmental policy and has as its object the operationalization of the Environmental Compensation tool and its contribution in supporting the management of the National System of Conservation Units (SNUC). The analysis seeks to contemplate the political and economic mechanisms that structure this system and then focus specifically on the UCs in the state of Rio de Janeiro, under the framework of the Fundo da Mata Atlântica (FMA). This research – and the aforementioned excerpt – is justified not only by the current importance of the theme, but also as an opportunity to discuss one of the mechanisms considered strategic by the public power, since, like others applied by environmental agencies, it is immersed in several controversies. The aim is to contribute to the discussion around issues involving the evaluation, origin, methodology, destination and effectiveness of resources arising from Environmental Compensation processes (CA) operated by the Mata Atlântica Fund (FMA) in the state of Rio de Janeiro and its contribution to the objectives of environmental conservation. Therefore, a qualitative methodology was chosen for the theoretical treatment of the theme and a quantitative one for the analysis of the financial and political dynamics of the application of the tool in the context of environmental conservation within the UCs located in the state of Rio de Janeiro. A bibliographic review was carried out on the subject of protected areas in Brazil, as well as surveys of Brazilian environmental legislation and the main institutional policies for the management of UCs. Primary and secondary data related to the application of the mechanism were also collected and organized, as well as data related to the profile of use and land cover of the UCs in the state of Rio de Janeiro, which were structured in tables, graphs and maps with the purpose of clarify the arguments discussed in the research. The completion of the dissertation allowed us to verify that, despite the advances and difficulties encountered in the subject, the application of the CA modality under study does not directly benefit the environment, based on actions of the same nature, that is, making available net biodiversity gain. However, its main function is allocated to the quantitative and qualitative management and maintenance of the SNUC, combating its main problems and adding more robustness and agility to the environmental policies for the creation and management of Conservation Units. After the analysis of the case study, the FMA, it was verified that this conferred considerable advances within the institutional field of the SNUC, adding support to the effectiveness of environmental policies of (re) adequacy, and above all, to the expansion of the territorial network of the SNUC.