Tandanus bellingerensis is distinguished from all its congeners (T. tandanus; T. tandanus; T. tropicanus; and T. bostocki) by the following combination of characters: 153-169, mode 159, rays in the continuous caudodorsal and anal fins; 35-39, mode 36, gill rakers on the first arch; and strongly recurved serrae on the posterior side of the pectoral-fin spine, which point to the distal end of the spine shaft. To a lesser degree, it also differs from T. tandanus of the MDB and eastern coastal drainages of Australia by a longer distance between the bases of the maxillary barbels (45.8-59.5% of SL, mean 53.2% vs. 39.5-48.8%, mean 44.9% and 37.2-48.9%, mean 42.8%, respectively). It can be further differentiated from T. tropicanus by having a smaller eye diameter (11.4-14.5% of HL, mean 13.5% vs. 14.7-18.5%, mean 16.3%, respectively) and, to a lesser degree, a shorter pectoral spine (8.8-11.8% of SL, mean 10.4% vs. 11.1-14.0%, mean 12.4%, respectively). It possesses brown or gray pigmentation on the lateral side of the head just posterior of the mouth, whereas T. tropicanus has a creamy-white or dirty-white patch extending ventrolaterally just posterior of the mouth. It further differs from T. bostocki by having a shorter post-orbital distance (37.9-42.3% of HL, mean 39.5% vs. 46.7-55.9%, mean 51.9%, respectively), a longer snout (48.6-54.5% of HL, mean 51.8% vs. 37.6-42.1%, mean 39.8%, respectively), and, to a lesser degree, a larger mouth gape (42.2-52.1% of HL, mean 48.1% vs. 32.5-42.4%, mean 38.3%, respectively) (Ref. 116005).