Barium appendicitis is a rare complication that has only been reported in a small number of case reports in the medical literature. A 57-year-old male presented to the emergency room with a sudden onset of sharp right lower quadrant abdominal pain. He had undergone contrast barium examination of his stomach 2 months previously as part of a periodic examination for gastric cancer. The radiological findings showed that the shape and radiopaque levels were similar to those of a dental metal crown silhouette. The patient was strongly suspected to have a localized intra-abdominal abscess due to ileocaecal perforation with a foreign body such as a dental metal crown. Emergency surgery revealed acute phlegmonous appendicitis. The resected specimen demonstrated a phlegmonous appendix which contained solid coproma. Pathological diagnosis and composition analysis confirmed the onset of appendicitis to be a result of the patient's ingestion of barium sulfate.