A 6-year-old girl was referred with acute chest pain and dyspnea. Transthoracic echocardiography revealed a single large well-defined intramyocardial cystic mass in the interventricular septum. A serologic test was positive for echinococcal infection. Urgent open heart surgery was undertaken to remove the cyst, and albendazole treatment was started. The postoperative course was satisfactory, and the patient was discharged on the 5th postoperative day without any complication.