Ampullary neoplastic lesions (ANLs) represent a rare cancer, accounting for about 0.6–0.8% of all gastrointestinal malignancies, and about 6–17% of periampullary tumors. They can be sporadic or occur in the setting of a hereditary predisposition syndrome, mainly familial adenomatous polyposis (FAP). Usually, noninvasive ANLs are asymptomatic and detected accidentally during esophagogastroduodenoscopy (EGD). When symptomatic, ANLs can manifest differently with jaundice, pain, pancreatitis, cholangitis, and melaena. Endoscopy with a side-viewing duodenoscopy, endoscopic ultrasound (EUS), and magnetic resonance cholangiopancreatography (MRCP) play a crucial role in the ANL evaluation, providing an accurate assessment of the size, location, and characteristics of the lesions, including the staging of the depth of tumor invasion into the surrounding tissues and the involvement of local lymph nodes. Endoscopic papillectomy (EP) has been recognized as an effective treatment for ANLs in selected patients, providing an alternative to traditional surgical methods. Originally, EP was recommended for benign lesions and patients unfit for surgery. However, advancements in endoscopic techniques have broadened its indications to comprise early ampullary carcinoma, giant laterally spreading lesions, and ANLs with intraductal extension. In this paper, we review the existing evidence on endoscopic diagnosis and treatment of ampullary neoplastic lesions.