Background: Endoscopic injection sclerotherapy (EIS) is an effective procedure for the treatment of esophageal varices. In the present study, the pathogenesis of gastric ulcer after EIS for esophageal varices was investigated. Methods: EIS for esophageal varices was performed for 610 patients in our department, and the frequency and clinical course of gastric ulcer after EIS were investigated retrospectively. EIS was performed using 5% ethanolamine oleate with iopamidol, which was injected intermittently under fluoroscopy. Results: Gastric ulcer after EIS for esophageal varices was observed in 14 of the 610 (2.3%) patients. These were located around the cardia of the stomach from the fornix to the gastric body. Gastric ulcer extended from the stomach lining into the esophagus in 11 of the 14 cases. Severe chest pain was observed, and dark purple mucosal changes of the esophagus and stomach were detected endoscopically at the time of injection in all 14 cases. All cases received dripping therapy, and prescription of a proton pump inhibitor. Gastric ulcer after EIS was refractory, and almost 2 months was required until the healing stage was reached. Conclusion: Gastric ulcer after EIS for esophageal varices is a rare but important complication of EIS.