A catfish (Pangasianodon sp.) presented to [XXX] for evaluation of a mass arising from the dorsal lip. The mass had appeared many months prior and changed in size. On presentation, the mass was approximately 1-cm in size, raised, with a wart-like appearance. CT with contrast was elected to determine the extent of the mass as described in the literature prior. The patient was anesthetized using MS-222 and a whole-body CT scan before and after intravenous contrast administration was performed. The patient declined under anesthesia and passed prior to surgery despite resuscitative efforts. The patient was sent for post-mortem at the same facility. On CT, findings included a well demarcated non-invasive cranial mass on dorsal lip; lens mineralization and ventral displacement OU; organized soft tissue opacity present in the caudal and ventral swim bladder; difficulty following digestive tract from esophagus to stomach, and from stomach to the beginning of the small intestine; and a separate air-filled structure from swim bladder. On histopathology, the mass examined was determined to be benign and compatible with granulation tissue. The eyes were found to have cataracts. The swim bladder was found to have severe, diffuse, chronic, granulomatous aerocystitis with epithelial hyperplasia, edema, and intralesional fungal elements. These elements were equally noted in the gills. Most of the anatomopathological findings were visualized on computed tomography. This is the first case describing computed tomographic features of mycotic aerocystitis in a catfish and the first published case demonstrating the use of contrast CT scan in a patient fish.