The objective of this research was to describe the structure of larval digenean communities in the freshwater snail Chilina dombeyana in Lake Mascardi, an oligotrophic Andean Patagonian lake. In total, 1,923 snails were collected during 2 sampling periods. Specimens were examined, and 8 digenean species were identified, all with allogenic life cycles. The snail infracommunities nearly always occurred as single-species infections, distributed mainly in the hepatopancreas. The double infections (0.2%) were always prepatent, and involved a schistosome and the notocotylid Catatropis chilinae. The overall prevalence, the prevalence of C. chilinae, and total species prevalence (without C. chilinae) significantly increased with snail size. Catatropis chilinae was the dominant species in all months and across all snail size classes. Maximum richness (6) was reached in the size class between 16 and 18 mm. Diversity indices, i.e., the Shannon-Wiener Index and the reciprocal of the Simpson Index, increased with snail size only during the second sampling period. No robust evidence of antagonistic interactions was found in the digenean community of C. dombeyana from Lake Mascardi.