Dissecting aneurysm of the ventricular septum as a complication after myocardial infarction (MI) is very rare. The patient was a 70-year-old women who was diagnosed with acute inferior MI. Three months after MI, catheterization showed a left ventricular aneurysm of the inferior wall, and left-to-right ventricular shunt flow was detected in the aneurysm. Echocardiography showed that the inferior left ventricular free wall was aneurysmal and dissected from the septal wall. Nine months after MI, chronic heart failure was uncontrollable by medication. At surgery, a tear (5 mm long) in the dissecting aneurysm of the ventricular septum was found and closed directly using 2 felt patches, and aneurysmectomy was performed using felt strips. The postoperative course was uneventful and she has been free from any complication for over 1 year.