This chapter investigates the role of institutional form and leadership in informing inter-denominational relations in the context of the Amazonian Yine people living in southeastern Peru. Approaching denominations as institutions provides a view on inter-denominationalism that pays attention to the role of materiality without excluding theological and sociocultural factors. The examination focuses on one Yine community counting with three different Christian churches: Evangelicals, Catholics, and Pentecostals. In the community, understandings of different churches as institutions worked as a platform for Christians to express their views on what constitutes legitimate kind of Christianity, and on the ways in which they considered themselves differing from other groups self-identifying as Christian. They therefore also served as grip surfaces for inter-denominational disputes. The spheres revealed central for these disputes and the negotiation of denominational boundaries were economics, education, and leadership.