A 43-year-old man was admitted to our hospital presenting with seizures and syncope. He had a history of a cold with a fever of 39°C occurring three days earlier. Electrocardiography (ECG) showed complete atrioventricular block (AV block) with a maximum pause of 32 seconds, for which temporary pacing was performed. Echocardiography showed mild hypertrophy of the left ventricle (LV) with a normal ejection fraction of 61%. Coronary angiography showed normal coronary arteries. Then, an endomyocardial biopsy was performed, the results of which indicated a diagnosis of acute myocarditis. After admission, the complete atrioventricular block disappeared together with normalization of the LV wall thickness.