Mycophagous gall midges in the family Cecidomyiidae (Diptera) are poorly known in Korea, with only 14 recorded species. From our sampling throughout South Korea during 2015-2017, we present evidence of the Korean distribution of another 20 species as follows-Lestremiinae: Anarete angusta Mo & Xu, 2009; Micromyinae: Anodontoceras saigusai Yukawa, 1967, Campylomyza appendiculata Jaschhof, 2015, Campylomyza furva Edwards, 1938, Peromyia gotohi Jaschhof, 2001, Peromyia pumila Jaschhof, 2001, and Tekomyia populi Möhn, 1960; Winnertziinae: Leptosyna nervosa (Winnertz), 1852, Winnertzia nigripennis (Kieffer), 1894, and Winnertzia solidaginis Felt, 1907; Porricondylinae: Bryocrypta indubitata Mamaev, 1964, Camptomyia flavocinerea Panelius, 1965, Coccopsilis obscura (Mamaev), 1964, Coccopsilis paneliusi (Yukawa), 1971, Cryptoneurus muscicola (Kieffer), 1896, Dirhiza abludentis(Mamaev), 1998, Divellepidosis separata (Yukawa), 1971, Larimyia lavalis Fedotova & Sidorenko, 2007, Parvovirga latostylata Jaschhof, 2013, and Porricondyla nigripennis(Meigen), 1830.