Monogenean parasites are often co-introduced with their fish hosts into novel areas. This study confirmed co-introduction of two dactylogyrids,Dactylogyrus squameusGusev, 1955 andBivaginogyrus obscurus(Gusev, 1955), and a newly described gyrodactylid species,Gyrodactylus pseudorasboraen. sp. into Europe along with their fish host, the invasive topmouth gudgeonPseudorasbora parva(Temminck & Schlegel) from East Asia. All three species were observed in the lower Dnieper and middle Danube basin regions and had slightly larger haptoral hard parts than the same parasites in their native range. While dactylogyrids occurred sporadically, we recorded regular infection byG. pseudorasboraen. sp. at relatively high prevalence and abundance. This latter species was observed in both the native and non-native range of topmouth gudgeon, and resemblesGyrodactylus parvaeYouet al., 2008 recently described fromP. parvain China. Both species were distinguished based on genetic analysis of their ITS rDNA sequence (6.6% difference), and morphometric differences in the marginal hooks and male copulatory organ. Phylogenetic analysis of dactylogyrid monogeneans showed thatB. obscurusclustered withDactylogyrusspecies parasitising Gobionidae and Xenocyprididae, includingD. squameus, supporting recent suggestions of a paraphyletic origin of theDactylogyrusgenus. In addition to co-introduced parasites, topmouth gudgeon was infected with a local generalist,G. prostaeErgens, 1964, increasing the number of monogeneans acquired in Europe to three species. Nevertheless, monogenean infections were generally lower in non-native host populations, potentially giving an advantage to invading topmouth gudgeon.