Anacanthorus Mizelle & Price, 1965 is the most diverse genus of Dactylogyridae and is characterized by the absence of anchors and bars in the haptor. Members of Anacanthorus are found parasitizing until now only fishes belonging to order Characiformes. Specimens of Brycon pesu Müller & Troschel, 1845 and Caenotropus labyrinthicus (Kner, 1858) were collected from Tocantins River, Brazil and had their gills removed and individualized in bottles containing water heated to (~65ºC), to relax and release the parasites, and ethanol absolute was increased to reach the concentration of 70%. The parasites found were collected and mounted in Hoyer´s medium. A new species of Anacanthorus, A. itaueirasensis sp. nov., is described from Brycon pesu, presenting the characteristics of Anacanthorus species parasitic on bryconids, as morphology of the copulatory complex, composed of a tubular MC...