Chylothorax is defined as an extravasation of chylous fluid to the pleural cavity due to various causes, and a spontaneous chylothorax associated with primary lymphedema is an exceedingly rare condition. We report a case of the chylothorax associated with lymphedema. A 14-year-old boy was admitted to our hospital for chest pain and dyspnea. He had been on medical treatment for lymphedema and his chest roentgenogram on admission revealed left pleural effusion. The diagnosis of chylothorax was confirmed by chemical analysis of the pleural fluid. The patient was treated successfully by ligation of the thoracic duct using video assisted thoracoscopic technique.