Resumo. Abstract Aim To evaluate the introduction of Oreochromis niloticus gill parasites in the Paranapanema River basin, northern Paraná, southern Brazil, as well as to inventory its occurrences in Brazilian fish farms and discuss the risks of transmission to native fauna. Methods The gills of 632 fish specimens from four fish farms in the Paranapanema Basin were analyzed. The parasites were collected, processed and identified according to specific procedure. Literature review was carried out to compile records of occurrence of gill parasites species in other Brazilian river basins. Results A total of seven (7) species of parasites were recorded, five (5) of the genus Cichlidogyrus, one (1) of Scutogyrus (Ancyrocephalidae, Monogenoidea) and one (1) of Lamproglena, Lamproglena monodi (Copepoda, Lernaeidae). All native from Africa. Some of these species have been reported in fish farms located in five other Brazilian watersheds. However, in this study a greater number of African gill parasite species was recorded in fish farms in northern Paraná (seven species), in the Paranapanema Basin, with Cichlidogyrus rognoni reported only for this basin. Conclusions The results confirm the introduction of these African parasites along with their host, O. niloticus, and the establishment of these species in Brazilian waters, since many specimens belonging to the species identified herein presented breeding activity for at least one period of the year. Although, only L. monodi has been recorded parasitizing Brazilian native species, data reported for other countries demonstrates the imminent risk of transmission of these O. niloticus parasites to native cichlids.