Abstract: This paper reports a capsalid species of monogenean in China. Nasicola klawei (Stunkard, 1962) Yamaguti, 1968 (Monogenea: Capsalidae) was found in the nosal capsule of longtail tuna, Thunnus tonggol (Bleeker, 1851), from Shanwei city, Guangdong Province. The specimens are basically consistent with the original description of Stunkard (1962) and the redescription of Yamaguti (1968) and Kohn et al. (2004) except for some differences in the structure of uterus, number of testes and the length of marginal hooks. This is the first time the genus Nasicola and species N. klawei are recorded in China, and the fish Thunnus tonggol is a new host. The specimens are deposited in the Lab of Fish Parasitology, College of Life Science, South China Normal University.