The most common cause of chylous effusion within the pleural space is considered idiopathic. Idiopathic chylous effusion is a diagnosis of exclusion which is only made once all other causes of chylous effusions have been ruled out. Other possible causes of chylous effusions include right heart disease, neoplasia, lung lobe torsion, heartworm disease, traumatic rupture of the thoracic duct, and diaphragmatic hernia. This paper describes the process required to diagnose idiopathic chylothorax in a 3.5 year old Goldendoodle, as well as the current treatments options and their outcomes.