Chylopericardial tamponade occurs very rarely after heart surgery. It may be the result of lymphatic duct interruption during mammary artery harvest, division of a large thymic remnant, or thrombosis of the subclavian or internal jugular vein by an indwelling central line. Although relatively straightforward when the pericardial aspirate has the usual milky appearance, the correct diagnosis can easily be overlooked particularly early after surgery when the patient is still fasting. We present a case report that illustrates the importance of sending all aspirates for chemical analysis irrespective of their color to arrive at the correct diagnosis and institute the appropriate medical management of this rare condition.