Gangliocytic paraganglioma is a rare tumor that occurs nearly exclusively in the second portion of the duodenum. This tumor is usually considered to be benign. So, endoscopic resection may be the best procedure to facilitate the diagnosis and for treatment to avoid an unnecessary, invasive operation. To the best of our knowledge, this is the first report of a periampullary gangliocytic paraganglioma that was successfully treated by endoscopic mucosal resection in Korea. We report here a case of a 45-year-old man who was found to have a periampullary gangliocytic paraganglioma. This tumor was adequately treated by endoscopic mucosal resection.