This paper focuses on the rise of the energy issue in the relations of Bolivia with Argentina and Brazil during the first decade of the twenty first century from a comparative viewpoint. In this context, the nationalization of Bolivian hydrocarbons decreed by Evo Morales on 1 May 2006 became a central point of the analysis in that it became a target and a political tool of the Movement for Socialism party (MAS). It proposes to investigate, on the one hand, the actions derived from this Decree within Bolivia and, on the other, the similarities and differences that have arisen in the negotiation processes and their results in the Argentine-Bolivian and Bolivian-Brazilian ties.