A new monstrilloid species belonging to the genus $Cymbasoma$ is described as a preliminary result from nocturnal surveys using a light trap on the east and south coasts of South Korea. Monstrilloid copepods are first recorded in South Korea. $Cymbasoma$ $striifrons$ n. sp. resembles $C.$ $striatum$ (Isaac, 1974) and $C.$ $tumorifrons$ Isaac, 1975 in sharing the character combination of transverse striations on forehead, somewhat small body (generally slightly less or longer than 1 mm), single lobed leg 5 bearing a short medial seta in female, and smooth lateral margin of anal somite without notch and wrinkles. However, $C.$ $striifrons$ n. sp. differs from $C.$ $striatum$ by relatively short and swollen cephalothorax, and rather strongly wrinkled genital somite. $Cymbasoma$ $striifrons$ n. sp. is also distinguished from $C.$ $tumorifrons$ in lacking a rounded protuberance on anterior margin of ventral surface and by relatively short cephalothorax and the number of ventral nipple-like processes on cephalothorax. Herein the new species is described and illustrated, with some comments on the morphological comparison with its allied species.