Gastric submucosal tumors (GSMTs) are frequently found incidentally on routine upper endoscopy. Definitive diagnosis based on histological confirmation is relatively difficult. Even without accurate diagnosis before treatment, open or laparoscopic surgery is considered the standard of care for most GSMTs. Alternatively, endoscopic resection of GSMTs using different techniques has been reported in a limited number of papers. We describe a case of an antral submucosal tumor, more specifically a leiomyoma of muscularis mucosa origin, in a 78-year-old woman, that was completely resected en bloc using an endoscopic submucosal technique with a TT-knife. It is suggested that ESD is a feasible option for the diagnosis and treatment of GSTMs.