A new species of leuconid cumaceans, Nippoleucon projectus n. sp. is described on the basis of the specimens collected from western shallow coast of the South Korea. This new species is easily distinguished from two previously recorded species (N. hinumensis and N. enoshimensis) in having the fifth abdominal segment prominently projected to rear at dorsal posterior portion and the carapace of the female with three spines on the frontal lobe.