A new genus, Paracosmocercella (Nematoda: Cosmocercoidea: Cosmocercidae), is proposed with monotypic Paracosmocercella rosettae n. sp. from the Japanese tree frog, Hyla japonica Günther, 1859, in Oita, Kyushu Island, Japan. Paracosmocercella resembles Cosmocercella and Cosmocercoides by having 2 rows of rosette papillae without plectanes ventrally in preanal region of male, but it is readily distinguished from Cosmocercella by lacking clear vesicle supporting rosette papillae and from Cosmocercoides by lacking rosette papillae in perianal region and having large-sized eggs, which hatch in uterus.