Nothobomolochus cresseyi sp. n. (Copepoda: Bomolochidae), a parasite from gills of the engraulid fish Engraulis anchoita Hubbs et Marini (Pisces: Engraulidae) from the coast of Argentina, is described and illustrated. The new species can be distinguished from other species of Nothobomolochus Vervoort, 1962 by the following combination of characters: three modified setae on the base of the antennule similar in length to the plumose setae, the nature of the armature of the third segment of the fourth endopod and the length and width of the thoracic somites 2 to 4 decreasing gradually. The new species represents the first record of this genus for Argentina.