Gastritis cystica polyposa is an uncommon lesion that usually occurs at the gastroenterostomy site, but it may also develop in the non-operated stomach. This malady is characterized by polypoid mucosal changes with hyperplasia and cystic dilatation of glands that infiltrate into the submucosal layer. We report here on a case of gastritis cystica polyposa that presented as a mass impacted in the duodenum in a 63-year-old male, and this patient had been admitted for evaluation of progressive epigastric fullness and dyspepsia. Esophagogastroduodenoscopy revealed that the partial duodenal obstruction was caused by impaction of a huge polypoid mass with a stalk that originated from the lower body of the stomach. We fished out the impacted mass with a forceps catheter while holding the neck with a snare catheter. Thereafter, an endoloop was applied to the stalk of mass, and this was followed by polypectomy using a snare catheter.