Examination of western tubenose goby (Proterorhinus semilunaris) from the River Dyje (Czech Republic, Danube basin) for metazoan parasites revealed the presence of metacercariae of Cyathocotyle prussica Mühling, 1896 (Digenea: Cyathocotylidae) in both muscle tissue and the peritoneal cavity. This is the first time that tubenose gobies have been reported as an intermediate host for C. prussica, and the first time that C. prussica metacercariae have been registered parasitising fish hosts in the Czech Republic. Here, we describe the morphology of metacercariae and five-day preadults, cultivated in vitro, and discuss the importance of recently established, non-native species as suitable hosts for this parasite.