Intrapericardial teratomas are rare after infancy. An accurate diagnosis can only be made with a high index of suspicion. Most of the time, a mediastinal teratoma ruptures/perforates the pericardial cavity, thus causing either pericardial effusion or life-threatening tamponade. These factors emphasize the importance of an early surgical excision even for extrapericardial locations. This report presents the case of a 16-year-old girl with intrapericardial teratoma who presented with cardiac tamponade which is a rare complication of this rare tumor with only eight cases reported so far beyond infancy. This patient presented with recurrent tamponade, and underwent multiple procedures of pericardiocentesis and developed pyopericardium and polyserositis. This intrapericardial teratoma was not detected by imaging modalities. © 2009 Springer.