Euchiloglanis longus differs from E. longibarbatus by having a pointed maxillary barbel, not elongated as a thread, with the tip only reaching to the gill opening (vs. the maxillary barbel elongated as a thread, with the tip reaching beyond the gill opening. Euchiloglanis longus differs from E. kishinouyei and E. longibarbatus by having one median indentation in the premaxillary tooth band (vs. indentations absent in E. kishinouyei, and E. longibarbatus with three indentations in the premaxillary tooth band, one in the middle and two on the sides. Euchiloglanis longus differs from E. davidi by having the length of the pectoral fin equal to 78.4–89.5% (vs. 90.5–117.1%) of the distance between the insertions of the pectoral and pelvic fins and from E. kishinouyei and E. longibarbatus by having the distance between the insertion of the pelvic fin and the anus equal to 108.9–140.6% (vs. 81.5–97.5 and 75.5–92.2%, respectively) of the distance between the insertions of the pectoral and pelvic fins. Euchiloglanis longus differs from E. davidi, E. kishinouyei and E. longibarbatus by having the depth of the caudal peduncle equal to 14.1–27.0% of the caudal-peduncle length (vs. 29.3–46.2, 28.2–34.3, and 26.8–44.5%, respectively). Euchiloglanis longus differs from E. dorsoarcus by having the anal-fin origin closer to the caudal-fin base than to the pelvic-fin origin (vs. the anal-fin origin closer to the pelvic-fin origin than to the caudal-fin base), and from E. phongthoensis by having the distance from the adipose-fin origin to the dorsal-fin insertion about 50% of the length of the adipose-fin base (vs. equal to the length of the adipose-fin base) (Ref. 86867).