Intramyocardial dissection following cardiac tumor excision is uncommon. The evidence available is limited to few case reports. ¹ Herein,we report an infant with large cardiac fibrosarcoma arising from the interventricular septum and underwent surgical excision.One month after surgery echocardiography revealed a cystic dissection located in the interventricular septum with residual shunts within the ventricular chambers. we performed conservative strategy due to the high surgical risk, difficulty of interventional therapy and hemodynamic stability.