Physalaemus cuvieri Fitzinger, 1823 occurs in Brazil, Paraguay and Argentina. In order to describe the helminth fauna of these anurans in southern Brazil, 68 specimens were captured in Campo Belo do Sul and Anita Garibaldi, State of Santa Catarina, and in Bom Jesus, State of Rio Grande do Sul, between May 2009 and January 2010. The anurans were taken alive to the laboratory where they were anesthetized and necropsied. Monogeneans identified as Polystoma cuvieri Vaucher, 1990 were found in the urinary bladder with a prevalence of 31.86% and a mean intensity of 2.06 helminths/host. In the same location of this study, other anuran species where captured and examined for helminths, but P. cuvieriwas found exclusively in Ph. cuvieri. This result may indicate a high parasite/host specificity.