Postoperative chylothorax after surgery for esophageal cancer is a rare but serious complication. Treatment initially consists of conservative therapy and, if it fails to provide improvement, it is important to perform surgical treatment without delay. We report on a recent case of intractable chylothorax. This report describes a 72-year-old man with Stage III esophageal squamous cell carcinoma. Subtotal esophagectomy, through a right thoracoabdominal approach with two-field lymphadenectomy, and cervical esophagogastric anastomosis via the retrosternal route, were performed. On the 12th postoperative day, a diagnosis of chylothorax was made. Conservative treatment was initiated, but it proved to be ineffective. Therefore, ligation of the thoracic duct via a thoracotomy was performed, but this was not effective, either. Lymphangiography undertaken to identify the site of the leak in the thoracic duct enabled a diagnosis of an extremely rare double thoracic duct and identification of the site of the leak in the thoracic duct, thereby allowing curative direct ligation of the site. This case underscores the remarkable usefulness of lymphangiography in dealing with intractable postoperative chylothorax. (J Nippon Med Sch 2017; 84: 268 273)