Pericardial effusions occur in approximately 30% of patients with untreated hypothyroidism. The effusions are more common in patients with longstanding, severe disease. But, cardiac tamponade is a very rare complication, because of the elasticity of pericardium and slow progression. We experienced a 61 year old female patient with cardiac tamponade due to primary hypothyroidism. She was treated with pericardiocentensis and thyroid hormone replacement, confirmed by echocardiography,thyroid function test and TRH stimulation test.