A 69-year-old woman was hospitalized because of a left-sided pneumothorax due to chronic obstructive pulmonary disease. During chest tube placement she developed hypotension and a decrease in peripheral oxygen saturation. A diagnosis of heart tamponade was made and the patient was treated successfully with pericardiocentesis and placement of a pericardial drain. Cardiac tamponade following chest tube placement is a rare and serious complication. When the clinical condition deteriorates following chest tube insertion, cardiac tamponade should be considered.