The purpose of this paper is to identify the motivations that led Brazil to adhere to processes of sub-regional integration. With that in mind, it tries to analyze the brazilian interests in the issues of security and international insertion, which has been a priority to the country. What is intended to demonstrate is the importance of the integrational processes, more specifically Mercosur, in the security politics. For this, it is necessary to comprehend how the economic integration in Latin America has been happening, and, more specifically, how had happened the approximation Brazil-Argentina in the decade of 1980. The agreements that conform South America as a zone of peace will also be studied. This way, utilizing a realist approach, through a vision from the periphery, it will be possible to conclude that the initiative of Mercosur is embedded in a brazilian effort in the security area.