Isolated cardiac location is an uncommon presentation of echinococcus (0.2 -3%), and involvement of the interventricular septum is even rarer. it may conduct to life-threatening complicationsincluding cyst rupture anaphylactic shock tamponade pulmonary, cerebral or peripheral arterial embolism acute coronary syndrome dysrhythmias infection ventricular or valvular dysfunction, as well as sudden death. The diagnosis is based on a range of arguments, here we report the case of a 15years old girl who was diagnosed to have a hydatid cyst of the interventricular septum , the presentation, management and follow-up of the patient is discussed.