Hyphessobrycon wosiackii is dintinguished from all its congeners, except H. amapaensis, H. ericae, H. heterorhabdus, and H. montagi, by having an humeral blotch continuous with midlateral stripe that becomes blurred posteriorly, not reaching beyond adipose fin (vs. humeral blotch, when present, not continuous with midlateral stripe, or stripe extending to caudal fin). It differs from H. amapaensis and H. heterorhabdus by having a caudal peduncle blotch (vs. caudal peduncle blotch absent); from H. ericae by having humeral blotch roundish (vs. humeral blotch vertically elongated); and from H. montagi by having a single humeral blotch (vs. two connected humeral blotches) (Ref. 116179).