Psilorhynchus khopai is a member of P. homaloptera species group and distinguished from its congeners in having the following combination of characters: 9-12 indistinct small dark brown round markings arranged in a longitudinal row on mid-lateral body, giving appearance of a faint brown lateral stripe; 7-9 unbranched rays on pectoral fin; 3 unbranched dorsal and anal fin rays; 9 + 9 principal caudal fin rays; forked caudal fin; 14-17 predorsal scale rows; 39-41 lateral-line scale rows; adpressed anal fin tip not reaching caudal fin base; and, in life, a faint gold stripe along dorsal midline with 4-5 black spots between dorsal fin and caudal fin base (Ref. 95676).

Description: Dorsal-fin rays iii,8; anal-fin rays iii,6; pectoral-fin rays vii,9 or viii,9 or ix,9; pelvic-fin rays ii,7; pelvic-fin origin vertical through, or slightly posterior to, dorsal fin origin; vertebrae 40 or 41, consisting of 27 or 28 abdominal and 13 caudal (Ref. 95676)