We experienced a serious complication of proximal stent strut penetration (PSSP) during thoracic endovascular aortic repair in a 74-year-old man who underwent two-stage hybrid treatment for a distal arch thoracic aortic aneurysm. First, a debranching right common carotid-left common carotid-left subclavian artery bypass was performed. Second, a TALENT Thoracic Stent Graft (Medtronic, Tokyo, Japan) was inserted at Zone 1 (Ishimaru). At deployment, a proximal bare strut accidentally everted and penetrated the aortic wall vertically. Postoperative computed tomography revealed that one crown of the proximal strut had penetrated the aortic wall vertically and had produced an intramural hematoma around the strut. The patient was observed carefully and discharged from the hospital without any sequelae. Seven months after the procedure, there was no remarkable change and his aneurysm was well excluded. PSSP can cause retrograde type-A aortic dissections. A bare strut tends to cause proximal strut penetration more frequently than a covered strut. More caution should be taken in the deployment of a stent graft with a bare strut.