Tumors of the major duodenal papilla, also known as ampullary tumor, are rare with an approximate 5% incidence of all gastrointestinal neoplasm. These tumors seem to be detected more frequently with increasing performance of upper endoscopic examination and endoscopic retrograde cholangiopancreatography (ERCP). Adenoma, most common benign disease of ampullary tumor, is very important because of its potential to undergo malignant transformation to ampullary cancer. Especially, endoscopic ultrasound or transpapillary intraductal ultrasonography can provide more detailed and accurate information on the extent of ampullary tumors and proper treatment should be done after diagnosis. Considering perioperative morbidity and mortality of surgical resection, endoscopic papillectomy is regarded as a curative treatment of ampullary adenoma. However, the indication of the procedure is very strict and there are various complications related to the procedure. Therefore, it is important to understand the role of endoscopy in diagnosis and treatment of ampullary tumor. In this review, the diagnostic role of endoscopy for ampullary tumor and the treatment method of endoscopic papillectomy will be discussed.