Gastrointestinal duplications can be found in all parts of the gastrointestinal tract. Duplications of the stomach comprise 2-8% of all duplications and are mostly diagnosed during the first year of life. We present a case of a gastric duplication cyst in a 29-year-old female, presenting with epigastric pain and vomiting. Preoperative diagnosis was assumed to be pyloric stenosis. Intraoperatively, a large mass that was attached to the greater curvature was found. Histopathology results were consistent with gastric duplication cyst.