Cardiac injuries caused by blunt chest trauma have a high mortality rate, and not only a median sternotomy but also a clamshell thoracotomy can be an alternative approach. In this report, we describe a case in hemostasis was achieved by clamshell thoracotomy in a left atrial appendage injury caused by blunt thoracic trauma. The patient is a 49-year-old woman. After an argument with her husband, she jumped off the balcony of her home on the 6th floor and fell in a supine position. She was brought to the hospital in shock, and pericardial effusion was found on FAST. She had cardiac arrest due to cardiac tamponade, and left anterolateral thoracotomy was performed to open the pericardium. After the removing the hematoma in the pericardial sac was removed, the patient experienced a return of spontaneous circulation, but a large amount of blood was seen spurting out, and the patient was transferred to a clamshell thoracotomy to secure the visual field. An injury of about 8 mm was observed in the left atrial appendage, which was sutured after establishing ECMO. The patient was discharged from the ICU on postoperative day 20 and discharged home unassisted on postoperative day 77. The cause of blunt cardiac injury is often traffic trauma, but this is a very rare case in which the patient suffered a left atrial appendage injury due to a fall trauma and clamshell thoracotomy was able to save her life. Therefore, clamshell thoracotomy is one of the options to open the chest in certain clinical situation.