Abstract: A two-year-old male Ragdoll cat presented with tachypnea and decreased appetite. Chest X-ray examination showed pleural effusion and right lung collapse; the puncture fluid extracted by thoracentesis was pinkish white, and the level of triacylglycerol in the puncture fluid was much higher than that of blood. The diagnosis of idiopathic chylothorax with lung collapse was confirmed by clinical examination and laboratory tests. After stabilization, the cat was operated on immediately by thoracic duct ligation with partial pericardial resection and placement of a chest drain. After stabilization of the cat, surgery was performed immediately with thoracic duct ligation and partial pericardiotomy, and a chest drain was placed. After surgery, the cat was closely monitored for fluid and gas accumulation in the pleural cavity. The drainage tube was removed on the 12 th day post surgery and the cat was discharged on the 18 th day. After eight months post surgery, a return visit showed that the affected cat was in good condition. The results indicated that surgery was an effective treatment for idiopathic chylothorax.