Caballerocotyla lenti n. sp. (Monogenea: Capsalidae), recovered from the gills of Auxis thazard (Lacépède) captured off the coast of Rio de Janeiro, Brazil, is described using light and scanning electron microscopy. The new species is characterized by: a tegument with 2-5 rows of dorso-marginal, unicuspid spines; 53-54 round testes; a constricted pharynx with numerous papillae on its border; and a haptor with a plicate marginal border, a central polygonal area and seven complete septa. C. manteri (Price, 1951) and C. gouri Chauhan, 1953 sensu Murugesh (1995) are figured and commented upon.