Chylothorax is a rare postoperative complication of congenital heart surgery. It has high morbidity with increased hospital stay and cost of treatment. Damage to the thoracic duct, disruption of accessory lymphatic vessels, and increased venous pressure exceeding that in the thoracic duct have been proposed as the possible causes of chylothorax after surgery for congenital heart disease. Prompt diagnose with early initiation of treatment will reduce the duration of drainage. Staged treatment is the general principle in managing this serious complication. Loss of chyle leads to volume, nutritional and electrolyte depletion, immunological deficiencies and hematological complications. Identifying the underlying cause and addressing it is crucial to definitive management.