Bilateral chylothorax is a rare complication after radical neck dissection. We report a case of bilateral chylothorax that developed after left radical neck dissection. A 40-year-old man was given a diagnosis of secondary left cervical lymph-node metastasis from left-sided tongue cancer (T1N0M0), and supraomohyoid neck dissection was performed. Since multiple lymph-node metastases had been found, modified radical neck dissection was performed. We ligated the thoracic duct because it ruptured intraoperatively. On the first postoperative day, a chyle leak was diagnosed, and the thoracic duct was ligated again. The chyle leak resolved, but on the fourth postoperative day, the patient complained of dyspnea and chest discomfort. Computed tomographic scans and chest X-ray films showed bilateral pleural effusions. Diagnostic thoracentesis was performed. Milky fluid was aspirated, and chylothorax was diagnosed. We used a conservative management approach, which involved total parenteral nutrition with total enteric rest. Repeated chest X-ray films showed no evidence of pleural effusion, and the patient was started to receive a low-fat diet on the 11th postoperative day. The patient had recovered completely.