Raillietnema lynchi n. sp. from the large intestine of a Rancho Redondo frog, Rana vibicaria, from Costa Rica is described and illustrated. Raillietnema lynchi n. sp. represents the twenty-third species assigned to Raillietnema and is distinguished from the 6 other Neotropical species by length of spicules (110–146 μm) and pattern of caudal papillae (4 pairs precloacal, 5 pairs postcloacal). Rana vibicaria also was found to harbor 1 species of Trematoda, Gorgoderina megacetabularis; 1 species of Cestoda, Ophiotaenia sp.; 4 species of Nematoda, Aplectana itzocanensis, Cosmocerca podicipinus, Falcaustra costaricae, and Rhabdias savagei; and 1 species of Acanthocephala represented by unidentified cystacanths.