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.