This study presents the first comprehensive helminthological data on three sympatric riparian mustelids (the European mink Mustela lutreola, the polecat M. putorius and the American mink M. vison) in south-western France. One hundred and twenty-four specimens (45 M. lutreola, 37 M. putorius and 42 M. vison) from eight French departments were analysed. Globally, 15 helminth species were detected: Troglotrema acutum, Pseudamphistomum truncatum, Euryhelmis squamula, Euparyphium melis and Ascocotyle sp. (Trematoda), Taenia tenuicollis (Cestoda), Eucoleus aerophilus, Pearsonema plica, Aonchotheca putorii, Strongyloides mustelorum, Molineus patens, Crenosoma melesi, Filaroides martis and Skrjabingylus nasicola (Nematoda) and larval stages of Centrorhynchus species (Acanthocephala). The autochthonous European mink harboured the highest species richness (13 species) followed by the polecat with 11 species. The introduced American mink presented the most depauperate helminth community (nine species). The prevalence and worm burden of most of the helminths found in M. putorius and M. lutreola were also higher than those of M. vison. Some characteristics of their helminth communities were compared to relatively nearby populations (Spain) and other very distant populations (Belarus). This comparison emphasized M. patens as the most frequent parasite in all of the analysed mustelid populations. It was possible to conclude that the invasive M. vison contributes to the maintenance of the life cycle of the pathogenic T. acutum and S. nasicola helminths, with possible implications for the conservation of the endangered European mink.