Brazil has been one of the most active actors in international environmental negotiations and is an up-and-coming developing country with huge reserves of natural resources, biodiversity, and ecosystems that are of interest to the rest of the world, such as the Amazon rainforest. This pa- per provides an analysis of Brazilian foreign policy in the area of environment. By studying three major, international environmental conferences – Stockholm 1972, Rio 1992, and the COP 15 in Copenhagen, in 2009 – from a liberal-constructivist perspective, the objective is to inves- tigate how Brazil has contributed to, as well as has been affected by, the international environ- mental regime over time. With the Rio+20 conference around the corner, this paper can provide important insights to what processes are behind Brazil’s action and position in these issues. The paper takes an eclectic approach and analyzes the national and international contexts and the positions Brazil took at the time of each conference, in the light of a framework that emphasizes the reciprocal relationship between domestic and international structure and agent. The conclu- sion is that there is a clear trend of Brazil going from being defensive and confrontational to being open to cooperation and taking initiatives. The changes in Brazilian attitude at each of the three conferences can be connected to great transformations in national as well as international context. The social and material reality in which Brazil has found itself has affected the way it interprets its capabilities, as well as how it identifies its interests. Furthermore, it is identified that tradition in foreign policy has played an important part in constraining some alternatives and promoting others.