Haematology has the potential to be a valuable tool in determining the health status of wild fish populations and wider ecosystem health. However, limited haematological data are available for wild Australian fish species, and the interpretation and nomenclature of leukocytes is variable and inconsistent in fish. The morphology and cytochemical reactions of erythrocytes, thrombocytes and leukocytes of 189 wild eel-tailed catfish (Tandanus tandanus), Wet Tropics tandan (Tandanus tropicanus), Hyrtyl’s tandan (Neosilurus hyrtlii), black catfish (Neosilurus ater), lesser salmon catfish (Neoarius graeffei), and silver cobbler (Neoarius midgleyi) are described. Erythrocytes, thrombocytes, lymphocytes, monocytes and heterophils in all six species are morphologically similar to those reported in other Siluriformes. Basophils and eosinophils are rarely reported in fish; however basophils were observed in peripheral blood smears of T. tropicanus and N. ater, and eosinophils were observed in N. graeffei. Periodic acid Schiff positive granular leukocytes were observed in N. graeffei, N. midgleyi, N. ater and T. tandanus. This is the first report on the leukocyte morphology and cytochemistry of any native Australian catfish species, and provides useful baseline data for future assessments of fish health and ecosystem integrity in Australia.