The phenomenon of Latin American integration has a long history. Throughout decades, a number of international organizations, regional and subregional blocs have formed in the region in order to unite interstate efforts aimed at fostering economic growth. The "pink tide" led to the emergence of several new integration projects that develop both political cooperation and trade and investment partnerships. The left-wing political forces managed to revise integration processes and enlarge a new integrational agenda with a number of issues from the field of economics, politics and social development. At the beginning of the 21st century, the integration reached a new level, turning from customs associations into political institutions, due to which the countries of Latin America began to acquire their own voice in the Western Hemisphere and beyond, to formulate regional and sub-regional development goals and consolidate their own foreign policy line. Some of the most important achievements of the integration process in early 21st century are the formation of the South American Union of Nations (UNASUR) - a promising regional body aimed at achieving political consensus and cohesion of economies, and creation of a single free trade zone. However, recent political shifts weakened the left-wing forces in Latin America, which resulted in a highly heterogeneous regional setting that has challenged a possibility of consensus achievement between regional governments. This could not but impact the regional integration projects, including UNASUR. Relying on official documents, media resources and vast range of special studies the present article analyzes the evolution of UNASUR with particular focus on the modern stage characterized by the authors as a crisis.