Distinguished from all members of Hypsolebias flavicaudatus complex, except H. nitens and H. sertanejo, by the presence of elongated bluish white spots on the posterior portion of the dorsal-fin base in males (vs. spots not elongated); whereas the spots are only slightly elongated in H. nitens and H. sertanejo, the spots in H. janaubensis are uniquely elongate, approximately as long as spots of the anterior portion of the fin. Can be separated from H. nitens and H. sertanejo by having the dorsal-fin origin on a vertical between the base of the first and second anal-fin rays in females (vs. between second and seventh rays), besides the dorsal-fin origin usually being anterior to anal-fin origin in males (vs. always posterior); and body more slender in males (body depth 33.9-38.4% SL vs. 39.7-43.2% SL; caudal peduncle depth 12.6-14.3% SL vs. 14.8-17.3% SL. Also differs from H. nitens, H. flavicaudatus and H. gilbertobrasili by having grey bars of flank narrower than interspace (vs. wider); from H. nitens, H. gilbertobrasili and H. guanambi, in having dorsal and anal-fin filaments reaching the posterior margin of the caudal fin (vs. reaching the basal portion of the fin); from H. nitens and H. flavicaudatus, in having the largest spots of middle portion of the flank larger than pupil (vs. smaller); and from H. radiseriatus, H. pterophyllus and H. flagellatus by having fewer dorsal fin filaments (2-3 vs. 4-6).