In this report, we present the rare case of a 53-year-old white female with a gastric duplication cyst. Diagnosis was made with a combination of CT scan and endoscopic ultrasound. The cyst was removed by using a seromuscular incision and enucleation. A review of English literature was performed to help define the etiology, workup, and treatment of adult patients. Theories of origin include embryologic enteric diverticula, incomplete notochordal plates separation, and embryonic longitudinal folds that fuse with a bridge. The essential features of duplication are that the cyst wall is contiguous with the stomach, is surrounded by smooth muscle, has a common blood supply, and is lined with epithelium. Few duplication cysts are diagnosed after the age of 12 and in adults present a diagnostic dilemma. In the past, preoperative diagnosis of gastric duplications was the exception, but with advances in imaging, most importantly endoscopic ultrasound, the diagnosis is established before surgery in a majority of the cases. Gastric duplication cysts have been removed using various methods; however, as enucleation can be performed easily with little disruption of normal anatomy, it should be considered the procedure of choice.