Species of Prochilodus Agassiz 1829 are among the most abundant fishes of South America basins and has good potential for pisciculture. During a study of the helminth parasites of Prochilodus lineatus (Valenciennes, 1837) (Characiformes) from Mogi Guaçu River, Brazil, a new species of Tereancistrum was collected. Tereancistrum pirassununguensis n. sp. can be distinguished from the other Tereancistrium species mainly by having a reduced accessory anchor sclerite with a little groove at the end; MCO as a sclerotized coiled tube forming two counterclockwise rings; an accessory piece as an inverted C, rod-like, not articulated at the base of the MCO; curved ventral bar; hooks similar with erect thumb and slightly curved shaft and point, slightly expanded shank proximally. This is the first record of a species of Tereancistrum in the southeastern of Brazil.