A 65-year-old woman was admitted with a complaint of a constant dull aching pain in the epigastrium for 4 days, with subsequent worsening and generalization of the pain. Clinically the abdomen was tender all over with board-like rigidity. Chest radiography revealed pneumoperitoneum and a decision was made to explore the patient. During laparotomy we found mild peritoneal collection with no perforation in the anterior surface of the stomach, duodenum, or the entire gastrointestinal tract. After opening the gastrocolic omentum, we found a large perforation of the posterior wall of the stomach. After direct repair with an omental patch, the patient recovered and was discharged after 14 days, with only wound infection. Posterior perforation of a gastric ulcer is a very rare condition.