A new species of the aleocharine genus Agaricomorpha Ashe (Coleoptera: Staphylinidae: Aleocharinae), A. ashei sp. nov., in Korea is described. A key to the known species of Agaricomorpha is provided. We also present the habitus illustration with line drawings of the diagnostic characters. This represents the third known Agaricomorpha species and the first occurrence of the genus in the Palaearctic region.