This bachelor s thesis intends to analyze Brazil’s participation in large environmental international meetings, with special emphasis in the formation of Brazilian Foreign Policy about this theme. For that purpose, Brazil s position during negotiations at the Rio-92 and Rio+20, chosen for this case study, is compared according to the two-level game theory of Robert Putnam. This research argues that tensions found at the external level, specially between developed and developing nations, as well as tensions at the domestic level, between environmental and ruralists groups, influenced for a conciliatory position, marked by the defense of the three pillars of sustainable development: environmental, social and economic, in which there is a search for legitimacy through the mediation between countries of the North and the South. After the 1990s decade, it is possible to observe a tendency of international preoccupation with new social themes that made it possible for the creation of various meetings. The United Nations Conference on Environment and Development or Rio-92, for example, determined a series of principles to guide environmental negotiations. In the year of 2012, the United Nations Conference on Sustainable Development or Rio+20 occurred with the following goals: resume with commitments made in 1992, debate the idea of a Green Economy, and establish a new institutional framework for sustainable development.