The aim of this chapter is to contribute to the understanding of the role of political leaders’ beliefs in shaping periods of cooperation and conflict in the Chilean-Bolivian rivalry. Specifically, the analysis employs the operational code framework to contrast the beliefs of Bolivian president Evo Morales regarding bilateral relations with Chile between his first and second presidential terms. In doing so, this research sheds light on the shift observed in Bolivia's foreign policy toward Chile from a relationship of relative trust during Morales's first term to a more confrontational approach in his second administration. Drawing on the foreign policy analysis literature, the results show that the change in Evo Morales's foreign policy behavior is associated with a process of learning in the form of a change in his beliefs regarding Bolivia's bilateral relations with Chile.