Gastric and intestinal mucosal hyperplasia and polyps are identified as a cause of morbidity and mortality in moray eels. This report describes the clinical presentations, diagnostic procedures, and therapeutic interventions in eight moray eels diagnosed with gastric polypoid hyperplasia. All described cases were humanely euthanized or found deceased, and multifocal adenomatous hyperplasia and polyps extending from the gastric mucosal epithelium were identified in all cases. The moray eels diagnosed with adenomatous hyperplasia and polyps often exhibited anorexia, regurgitation, and occasional changes in buoyancy, and supportive care was unsuccessful in alleviating or resolving these signs.