We describe a case of frozen elephant trunk deployment unintentionally malpositioned into the false lumen. An 83-year-old man underwent total arch repair with a frozen elephant trunk for type A acute aortic dissection complicated by mesenteric malperfusion. However, intraoperative transesophageal echocardiography showed expansion of the false lumen in the descending aorta, suggesting a malpositioned frozen elephant trunk into the false lumen. Endovascular fenestration of the dissecting flap and subsequent endograft deployment from the inside of the malpositioned frozen elephant trunk graft to the true lumen of the descending aorta was successfully performed under intravascular ultrasound guidance.