Chylothorax is a rare yet serious complication after coronary artery bypass grafting (CABG), with a poor prognosis, unless left untreated appropriately. A 70-year-old male patient, who underwent CABG with internal thoracic artery and saphenous vein grafts three weeks prior was admitted to the emergency service with severe dyspnea and shock. Chest X-ray revealed left-sided massive pleural effusion. The patient was diagnosed with tension chylothorax and a left tube thoracostomy was performed. The patient was then discharged with conservative treatment.