The goal of this paper is to analyze and reassess the criteria according to which a class of postpositions is distinguished in the Beserman dialect of Udmurt. This class is traditionally divided into inflected and non-inflected postpositions. Analysis of syntactic and morphosyntactic properties of these two subclasses shows that items traditionally labeled as inflected postpositions form a homogeneous group and show noun-like behavior in most cases, while non-inflected postpositions are heterogeneous. Based on this analysis, we propose to single out a part-of-speech class of relational nouns and show that the rest of the postpositions could be further divided into subclasses with different behavior. The study is based on the data obtained during fieldwork in 2009–2015 in Udmurtia (for Beserman) and on corpus data (for literary Udmurt).