Pseudancistrus zawadzkii can be distinguished from all known congeners, except members of the P. barbatus group, by the possession of hypertrophied odontodes along the snout margin and the absence of evertible cheek plates. It further differs from other congeners by the combination of the following characters: whitish spots that abruptly increase in size between the head (diameter 1.1-1.3 mm) and body (diameter 2.6-3.0 mm); odontodes along margin of snout increasing gradually in length from posterior of snout tip to cheek; longest odontodes on posterior most portion of non-evertible cheek plates.; rounded spots that do not cover more than one plate along the body; head depth 67.0-72.7% of HL; cleithral width 35.2-38.0% of SL; distance between posteromedial margin of supraoccipital and dorsal-fin origin 6.7-9.2% of SL; anal-fin spine length 11.9-13.8% of SL; peduncle depth 12.5-14.2% of SL; and internares distance 12.7-16.6% of HL (Ref. 95679).