The parasitic nematode Pseudoterranova cattani sp. nov. is described from the stomach of the South American sea lion Otaria byronia De Blainville, sampled along the coastline off central-south Chile, between 1980 and 1997. The adult and larvae of this species have been previously reported in the Southeastern Pacific Ocean as Phocanema decipiens Myers. Major differences with species from the North Atlantic and Northwest Pacific are based on the body size, number, distance and size of caudal pillae