Chylopericardium is an uncommon but serious complication after open heart surgery that often necessitates surgical treatment. We describe a case of continuous and severely symptomatic chylous pericardial effusion after coronary artery bypass grafting in which the diagnosis was established by lipid electrophoresis. Initial conservative management failed, and ligation of the thoracic duct and pericardial fenestration were finally required for a successful outcome.