Esophageal achalasia is often associated with esophageal cancer. However, in many cases, esophageal cancer tends to be found in an advanced stage, with a poor prognosis. However, early-stage cancer was detected recently due to the advances in endoscopic instruments. In those cases, it is important to facilitate successful treatment by endoscopic submucosal dissection. We analyzed a total of six cases of esophageal cancer with achalasia in four patients treated with endoscopic submucosal dissection. Three features common to all six cases had a bearing on how endoscopic submucosal dissection was performed. First, esophageal dilatation and diminished peristalsis facilitated the performance of successful endoscopic submucosal dissection. Second, the esophageal wall was thickened, primarily with muscular tissue. Third, the submucosal layer contained abundant blood vessels that made it difficult to minimize bleeding during dissection. Those findings suggest that endoscopic submucosal dissection for early esophageal cancer associated with achalasia is a safe and potentially curative procedure. It is important, therefore, to detect esophageal cancer early.