The case is a 33-year-old white female presenting with a 3-day history of abdominal pain. On initial examination, she was found to have significant right lower quadrant tenderness. Workup included computed tomography, which demonstrated a large cystic mass appearing to be of ovarian origin. The patient required an exploratory laparotomy, at which time she was found to have a large cyst involving the lesser curvature of her stomach. The cyst was successfully resected, and the patient had a rapid postoperative recovery with complete resolution of symptoms. Histopathologic evaluation of the specimen identified a mesenteric cyst. Mesenteric cysts are uncommon; gastric involvement is exceedingly rare. A review of the literature is presented.