Can be diagnosed from all its congeners, except Moenkhausia heikoi and Moenkhausia phaeonota, by having a dark, broad longitudinal stripe from the opercle to the end of caudal peduncle. Differs from Moenkhausia heikoi mainly by possessing 18-21 branched rays on anal fin (vs. 24-26), by the absence of a round blotch at the end of the caudal peduncle (vs. present) and by the dark stripe formed by relatively small chromatophores (vs. large chromatophores). Can be separated from Moenkhausia phaeonota by the anterior portion of longitudinal band darker at horizontal septum (vs. darker below horizontal septum), the deep dark pigmentation along horizontal septum extending anteriorly up to humeral region (vs. extending up to vertical through pelvic-fin origin), number of vertebrae 34 (vs. 36-37), more dispersed dark stripe, not well delimited (vs. less disperse, relatively well delimited), the melanophores of interradial membrane between first and fifth branched dorsal-fin rays restricted to the edge of lepidotrichia (vs. spread over interradial membrane), the distance between snout to pelvic-fin origin 46.9-50% SL (vs. 43.2-46.6), the distance from snout to anal-fin origin 62.1-65.4% SL (vs. 55.9-61.2), the anal-fin base length 25.1-28.4% SL (vs. 28.5-33.8) (Ref. 85160).

Description: Dorsal-fin rays ii,9; anal-fin rays iv or v, 18, 19, 20, or 21; pectoral-fin rays i,10, 11, or 12; pelvic-fin rays i,7 (Ref. 85160).