The genus Acymatopus Takagi is reported for the first time from Korean fauna along with two nominate species, A. minor Takagi, 1965 and A. takeishii Masunaga, Saigusa & Yang, 2005. This genus belonging to the subfamily Hydrophorinae in the family Dolichopodidae, is comprised of only six species in the world and distributed only in Japan and China yet. Both adults and larvae of this genus are known to be found on rugged and rocky marine shores of the tidal zone. The authors found the first recorded species in the west seaside of Korea, where many barnacles are inhabited. The descriptions and illustrations of external features including male genitalia of newly recorded species are provided here.