Left ventricular mural thrombi can occur in setting of acute myocarditis. Major thromboembolism may occur according to the echocardiographic characteristics of the thrombi. Mobile, irregular and protruding thrombi are known to raise systemic embolism more easily than immobile laminar clot. We experienced a case of a hypermobile pedunculated left ventricular thrombus complicated to acute myocarditis in a 49-year-old woman. Mobility of it increased day by day in spite of the proper anticoagulation. Surgical removal of the thrombus was performed to prevent major thromboembolism.