An adult male frilled lizard (Chlamydosaurus kingi) was found dead in Northern Territory (Australia). On physical examination it was found to be severely emaciated. At necropsy the stomach was found to be firm with mild thickening of the gastric mucosa. Gastric rugae were prominent and the mucosa was red with a thin layer of dark red mucus on its surface. Light microscopic examination revealed a mild diffuse gastritis with infiltration of the lamina propria by lymphocytes, plasma cells, and heterophils. Large numbers of small, round amphophilic to basophilic (2 to 4 μm in diameter) organisms morphologically consistent with Cryptosporidia were seen on the surface of the mucosal epithelium and free in the gastric lumen. The gastric lesions seen in this frilled lizard did not involve atrophy, as previously described in lizards with gastric cryptosporidiosis, and were similar to those described in snakes. The possibility that more than one species of Cryptosporidium parasitizes reptiles could explain the different lesions. This is the first report of cryptosporidiosis in a frilled lizard.