A semicircular esophageal cancer, approximately 7 cm wide, was detected in the middle to lower esophagus of an 81-year-old gentleman during an esophagogastroduodenoscopy. Thorough examinations using chromoendoscopy and endoscopic ultrasonography led to preoperative diagnosis of an intramucosal tumor. With informed consent, the patient underwent endoscopic submucosal dissection (ESD), a novel endoscopic treatment. A successful en bloc resection by ESD was completed without complications. The resected specimen measured 72 mm by 35 mm, and the cancer was contained in an area of 66 mm by 32 mm. Histologic assessment revealed squamous cell carcinoma, microinvasive into the mucosal layer, but without vessel infiltration. Six months after ESD, mild stenosis remained, but dilation was no longer needed, and esophagogastroduodenoscopy with chromoendoscopy and biopsy revealed no residual or recurrent cancer.