We herein report two cases of perigraft effusion mimicking graft infection after debranching thoracic endovascular repair for an anastomotic pseudoaneurysm of the distal ascending aorta. Both patients presented with a bulging tumor on the sternum. Enhanced computed tomography showed no endoleak, but extension of periprosthetic graft fluid to a subcutaneous sternal wound was present. We suspected a deep sternal wound infection; however, cultures of débrided tissues were negative. After drainage of the subcutaneous fluid or negative pressure wound therapy, both patients were doing well without recurrence of effusion. Endotension was considered to have been associated with enlargement of the perigraft effusion.