A new species of nematode, Pseudodelphis chilensis n. sp., is described. This parasite was found in muscles of the pectoral fins of a blenniid fish, Scartichthys viridis, from central Chile. The new species differs from the other 2 described (P. oligocotti Adamson and Roth, 1990 and P. limnicola Brugni and Viozzi, 2006) for its longer glandular esophagus and a small caecum at the beginning of the glandular esophagus; both characteristics are in males and females. In addition, the male of P. chilensis n. sp. does not have an adanal caudal papillae, and it has longer spicules than the other 2 species. This is the first Pseudodelphis species described for Chile and the second for South America.