The UN Declaration on the Rights of Indigenous Peoples recognizes Indigenous peoples’ rights to self-determination and to maintain their distinct institutions. This article investigates how those rights are being exercised in Charagua, which became Bolivia’s first “Indigenous autonomous government” when the municipality’s Guaraní majority approved conversion in 2015. We explore the construction of novel institutions of self-government to assess how local Guaraní leaders are negotiating autonomy, both externally and internally. The result of those negotiations is a hybrid political system in which power is balanced between an executive organ (as required by Bolivian law) and a deliberative assembly (the Ñemboati Guasu, which operates according to Indigenous custom). The prominence of the assembly expresses a significant form of autonomy that promotes intercultural political participation and enacts Indigenous self-government in ways that are important to Guaraní people. Yet, because the new political unit does not control subsoil rights and thus cannot determine the sorts of development that take place in its territory, we cannot yet say the Guaranís are exercising full and robust autonomy as expressed by the UN Declaration’s provisions for self-determination.