As a result of the faunistic survey of the free-living marine nematodes from coastal algal beds and sublittoral sands in South Korea, we report a meiobenthic species, Desmoscolex cosmopolites Timm, 1970, for the first time from the western Pacific as well as Korean waters. Among 17-ring Desmoscolex species, D. cosmopolites is represented by the following combination of characters: absence of subventral setae on 10th and 14th main rings and the presence of subdorsal setae with large angular lance-shaped tip. A detailed morphological redescription is provided using a scanning electron microscope and a differential interference contrast microscope. Character comparison between D. cosmopolites and its allied congeneric species is also analysed.