Horadandia brittani can be diagnosed from its congener H. atukorali by the combination of the following characters: deeper body (depth 27.7-31.9 % SL, vs. 24.6-29.8); dorsal profile of head approximately straight (vs. concave) behind level of eye; lesser eye diameter (27-37 % HL, vs. 37-41); origin of dorsal fin distinctly behind (vs. slightly posterior to) origin of pelvic fin; pelvic fin just reaching (vs. reaching beyond) origin of anal fin; origin of dorsal fin located closer to hypural notch than to snout tip (vs. dorsal-fin origin located halfway between snout tip and hypural notch); a lateral process on side of kinethmoid absent (vs. present); palatine process of maxilla obtuse (vs. acute); and supraorbital length ~44 % eye diameter (vs. ~50 %) (Ref. 94541).