For the Amazonian Yine people, Christian denominationalism provides an important means for organizing social life. Denominations in this context are not, however, to be understood as clearly bounded entities. Simultaneously with forming and renewing denominational boundaries, the Yine continuously cross, dissolve, and redefine them. This article attempts to understand the denominational dynamics among the Yine people, and in particular their back and forth movement between Evangelicalism, Catholicism, and Pentecostalism, without viewing their denominational allegiances as subordinate to other forms of social organization or as something religiously insincere. Seeking inspiration from the ethnography of personhood and humanity in Amazonia, it suggests that denominations among the Yine can be understood to exist as unstable forms of belonging, as “thickenings” of different kinds of Christian moral relations to sociality, that take place on a continuum pictured not as a line but rather as a space. At the more general level the article shows how Christian vernacular denominationalism is likely to not be based on dogmatic differences but to be rather something that comes to be in practice. Furthermore, the article makes explicit how denominational boundaries are not always of the one and the same kind everywhere but vary between denominations.