Oryzias soerotoi is distinguished from all congeners from Sulawesi by its brilliant orange coloration in the dorsal and ventral margins of the caudal fins of adult males. It differs by fewer scales along lateral midline (30-32) from O. sarasinorum (70-75), O. bonneorum (36-39), O. eversi (33-36), O. orthognathus (45-57), O. nigrimas (34-37), and O. matanensis (41-47). Other character useful to identify O. soerotoi is by having deeper body depth (21.6-24.8 vs. 13-15 in O. sarasinorum; and 17-20 in O. bonneorum). In addition, O. soerotoi has narrower body than O. matanensis (26.0-31.0) and O. profundicola (30.4-35.2); fewer dorsal-fin rays (8-9) than O. sarasinorum (11-12), O. bonneorum (12-13), O. eversi (10-12), and O. profundicola (10-14); fewer vertebrae (29-31) than O. sarasinorum (34), O. orthognathus (33), and O. nigrimas (32-33). It can be diagnosed from O. matanensis, O. marmoratus, O. profundicola, and O. hadiatyae, by the absence of dark brown blotches or bars on the lateral body in adult males. It can be further distinguished by its shorter anal-fin base (23.7-29.7) from O. marmoratus (31.4-36.9) and O. profundicola (37.4-41.4). It is distinct from O. hadiatyae by its short head (21.9-24.9 versus 27.2-37.1) and no pronounced concavity on the snout; from O. celebensis by the absence of distinct black stripes from the posterior midbody onto the caudal fin and of diffuse dark bars extended from dorsal and ventral to the midline; further from O. celebensis by having somewhat fewer pectoral-fin rays (9-10 vs. 10-11); from O. woworae, O. wolasi, and O. asinua by the absence of steel blue body coloration and of brilliant red or orangish coloration in the dorsal and ventral margins of the caudal peduncle; and larger size than O. woworae, O. wolasi, and O. asinua (up to 3.21 cm SL vs. 2.86 cm SL); from O. nebulosus by having a truncate caudal fin (vs. emarginate) and somewhat fewer lateral scales (30-32 vs. 32-36). It differs from O. mekongensis and O. pectoralis, Oryzias outside of Sulawesi having orange or reddish margins on the caudal fins of males by the possession of 8-9 dorsal-fin rays (vs. 5-7 in O. mekongensis and 6-7 in O. pectoralis) and attaining larger size (up to 1.67 cm SL in O. mekongensis and 2.23 cm SL in O. pectoralis) (Ref. 103734).