Most patients with ampullary carcinoma have obstructive jaundice without cholangitis. We experienced a patient with ampullary carcinoma who presented with obstructive jaundice and cholangitis, probably because of an accompanying periampullary choledochoduodenal fistula. A 77-year-old Japanese man had jaundice, high fever, and upper abdominal pain and was diagnosed, at another hospital, with obstructive cholangitis. On admission to our hospital, his symptoms and signs had subsided spontaneously. Abdominal ultrasonography showed cholecystolithiasis and dilatation of the common bile duct. Duodenoscopy showed an ulcerating tumor at the oral prominence of the ampulla of Vater and a periampullary choledochoduodenal fistula at the bottom of the ulcer. Biopsy from the fistula showed well differentiated adenocarcinoma. With a diagnosis of ampullary carcinoma with fistula formation, the patient underwent pylorus-preserving pancreatoduodenectomy. The diagnosis was confirmed by histology. This communication presents a unique case of ampullary carcinoma that caused obstructive jaundice, which subsided spontaneously but was associated with cholangitis caused by the divergent effects of the periampullary choledochoduodenal fistula formed by the carcinoma.