BACKGROUND Brunner's gland adenoma (BGA) is a rare benign duodenal tumour proliferating from Brunner's glands. Here, we present a giant BGA leading to anaemia, with its clinical, endoscopic, radiological, surgical and pathological findings. METHODS A 48-year-old Turkish man complained of a six months history of vague epigastric discomfort, loss of appetite and nausea after meals without vomiting. The physical examination had no unremarkable finding. Laboratory findings, including liver function tests, were within normal limits except a hypochromic, microcytic anaemia. The upper gastrointestinal endoscopic examination revealed a lobulated, red, polypoid tumour with a smooth surface covered with normal mucosa. The tumour was located on the anterior surface of duodenal bulb and had a wide base measuring 3.5 × 4 cm in size. Endoscopic ultrasonography revealed a submucosal polypoid mass located at the anterior surface of duodenal bulb. The endoscopic excision was tried but was not successful. The patient was operated and transduodenal polypectomy was done. The postoperative period was uneventful and the pathologic diagnosis was assessed as Brunner's gland adenoma. During the follow-up period, the endoscopic examination was normal at 12th month postoperatively. CONCLUSIONS BGA is a rare benign cause of anaemia that can be treated with excellent results.