A mysid species, Parastilomysis paradoxa Ii, 1936 belonging to the subfamily Mysinae Hansen, 1910 which comprises approximately 90% of all mysid species, is newly reported from Korean waters. The genus Parastilomysis Ii, 1936 which is also new to Korea, is distinctly different from other genera by having biramous third and fourth pleopods of the male, and telson with an apical cleft. In the present paper, authors provide detailed descriptions and illustrations of P. paradoxa based on the specimens collected from the southern coast of the Korean peninsula, and also discuss on the zoogeographical distribution herein. Parastilomysis paradoxa belongs to Mysidae Haworth, 1825, and is the 50th species in Korea.