Herein, we report a new species of leptostracan, Nebalia koreana (Malacostraca) collected from the southern and eastern coasts of the Korean peninsula. All the specimens of this species were collected by means of light traps from harbors where the bottoms are sandy and with algal mats. The new species differs from all other known Nebalia in the following characters: the carapace is relatively small, and covers the lateral sides of pleonite 2 and partially the lateral sides of pleonite 3; the fourth article of the antennule has up to five short distal spines; pleonites 3 to 7 have rounded denticles along the posterior dorsal borders; the epipod of thoracopod 7 bears 5 to 6 plumose setae along the posterior margin, which are lacking on the remaining thoracopods; and the protopod of pleopod 4 lacks serration along the posterior border. Only two species of Nebalia have been reported from the tropical or subtropical seas of Asia. Therefore, the new species is the first species of Nebalia found in the temperate zone of Asia. Additionally, type localities and world distribution of the genus Nebalia are provided in this paper.