We report a rare case of adenocarcinoma of the duodenum arising from Brunner's gland. A 70-year-old man with a history of hypertension was referred to us with the complaint of abdominal discomfort. Upper gastrointestinal endoscopy revealed an irregular elevated mucosa and a submucosal tumor with delle in the duodenal bulb. Biopsy specimens revealed adenocarcinoma (the former) and hyperplasia (the latter). We could not agree with the patient about performing pancreaticoduodenectomy, so under the diagnosis of primary duodenal carcinoma, we performed resection of the bulbus and the antrum. Pathological examination showed that one of the tumors was consistent with normal Brunner's glands, Brunner's gland hyperplasia and adenocarcinoma arising from Brunner's glands. The patient's postoperative course was good, but 15 months after, he developed lymph node recurrence at the site of the pancreas head. Under the diagnosis of lymph node metastasis of duodenal cancer, we performed pancreaticoduodenectomy this time. Pathological examination confirmed our preoperative diagnosis. The patient remained well after the surgery for 2 years.