The aim of this study was to examine the causes of cardiac tamponade in children undergoing percutaneous pericardiocentesis. Patients who presented with other complaints but were diagnosed with cardiac tamponade based on clinical and echocardiographic findings between January 2010 and January 2013 were retrospectively investigated. Electrocardiography, telecardiography and transthoracic echocardiography were performed. Pericardiocentesis was performed percutaneously under continuous blood pressure and rhythm monitoring with echocardiography and fluoroscopy. Pericardial fluid was analyzed on hemography and biochemistry. Fourteen patients (six boys, eight girls; median age, 7 years) underwent pericardiocentesis for cardiac tamponade. At presentation, 78% had dyspnea, 56% chest pain, and 49% fever. All had cardiomegaly, and their cardiothoracic index was 0.56-0.72. Also, all patients had sinus tachycardia; 78%, low QRS voltage; 70%, ST-T changes; and 50% QRS alternans. On echocardiography the widest diameter of pericardial effusion was between 12 mm and 36 mm depth around the heart. The pericardial fluid was purulent in one, serohemorrhagic in seven, serofibrinous in two, and serous in four cases. Pericardiocentesis was unsuccessful in two patients, who underwent open surgical drainage, with no complications. Based on pericardial fluid characteristics and additional tests, cardiac tamponade was caused by an infection in five patients, hypothyroidism in two, familial Mediterranean fever in two, malignancy in one, acute rheumatic fever in one, collagen tissue disease (systemic lupus erythematosus) in one, catheter placement-associated damage in one, and idiopathic pulmonary arterial hypertension in one patient. Pericardial effusion and cardiac tamponade in children have varied causes, and early treatment is life saving.