A 68-year-old woman was diagnosed with leiomyosarcoma (LMS) based on preoperative biopsy of the gastric body. As tumor invasion confined to the submucosa with no breaking of the submucosal layer was confirmed on endoscopic ultrasonography (EUS), the patient underwent endoscopic submucosal dissection (ESD) for gastric LMS, resulting in complete tumor resection. No apparent recurrence was observed in the 2.5 years after treatment. This is an extremely rare case of gastric LMS that underwent ESD after a precise preoperative diagnosis, with no signs of recurrence after treatment. ESD may be an acceptable option for gastric LMS when EUS findings allow this treatment method.