A new species of Paracrenhydrosoma (Copepoda: Harpacticoida: Cletodidae) is described from samples taken from muddy bottoms in Jangmok, Geoje Island, Korea. The genus Paracrenhydrosoma is distinguished from other genera of the Acrenhydrosoma-complex (Acrenhydrosoma, Dyacrenhydrosoma and Neoacrenhydrosoma) by carrying an antennal exopod with two setae, P1 endopod with three setae, P3 endopod with two setae and P5 exopod with two setae. The new species differs from its congeners as follows: bifid rostrum on anterior margin, long caudal ramus, exceedingly long baseoendopodal mucroniform process of female P5 that reaches the end of the second free abdominal segment, and modified P3 endopod of male. A tabular key to aid in the identification of the Acrenhydrosoma-complex is provided. The worldwide distribution of the Acrenhydrosoma-complex is summarized and discussed.