Liobagrus hyeongsanensis can be distinguished from all other species of Liobagrus by having a smaller size (a maximum of 9.0 cm SL, vs. 15.0-18.0 cm); a smaller number of eggs per gravid female (60-110 vs.130-210); and a smaller number of serrations on the pectoral fin (2-3, mostly 3, vs. 3-6 or 0-3, smaller or vestigial); a slenderer body width at pectoral-fin base (15.5-17.9 % SL, vs. 17.1-21.9%); a relatively short pectoral spine (3.7-6.5 % SL, vs. 6.8-13.1%). It also differs from all congeners by its lower jaw shorter than the upper jaw (vs. longer or equal), and body and fins entirely brownish yellow without any other markings (vs. a vertical broad yellowish crescent-shaped band on the caudal fin or black or whitish yellow outer margins of the dorsal and anal fins) (Ref. 104914).