Nematodes of the genus Physaloptera are common in rodents, including in species of the Family Cricetidae. There is no report of nematodes parasitizing Cerradomys goytaca, so this is the first one. For this study, 16 rodents were captured in the city of Quissam, in the northern of Rio de Janeiro State. The rodents were necropsied, and the digestive tracts were analyzed under a stereomicroscope for the presence of parasites. The nematodes were fixed in hot AFA, clarified in Amann's lactophenol, mounted on slides with coverslip, and observed under an optical microscope. Part of the nematodes was fixed in Karnovisk solution for scanning electron microscopy. Nematodes presented evident sexual dimorphism. Oral openings had two semicircular pseudolabia, with an external lateral tooth and an internal lateral tripartite tooth on each pseudolabium. Males had a ventral spiral curved posterior ends with the presence of a caudal alae with 21 papillae with four pairs of pedunculated papillae arranged laterally, three pre-cloacal sessile papillae arranged rectilinearly and five pairs of post-cloacal sessile papillae. There was also a pair of phasmids located between the fourth and fifth pairs of post-cloacal papillae as well as two spicules that were sub-equal in size but of distinct shapes. The females have five uterine branches. The morphological and morphometrical analyses of the nematodes collected from C. goytaca were compared with other species, and the results indicated that this is a new species of the genus Physaloptera, Physaloptera goytaca n. sp.
