The cardiovascular manifestations of hyperthyroidism are sinus tachycardia, paroxysmal supraventricular tachycardia, atrial fibrillation, atrial flutter, atrioventricular block, bundle branch block, angina pectoris, heart failure, and cardiomyopathy. Though complete atrioventricular block is rare, it is important to recognize it in clinical practice because of the possibility of cardiac arrest. We experienced a 47-year-old female patient who had hyperthyroidism with complete atrioventricular block and developed cardiac arrest despite the initiation of an antithyroid drug. We could resuscitate successfully and inserted a temporary pacemaker, but eventually a permanent pacemaker was needed to prevent the recurrence of cardiac arrest. We report a rare case of complete atrioventricular block and cardiac arrest associated with hyperthyroidism with the review of references.