Prior studies have shown that a bird-beak configuration causes serious complications after thoracic endovascular aortic repair (TEVAR). However, factors that cause bird-beak configurations are poorly understood. The purpose of this study was to assess the influences of anatomical and device-related factors on bird-beak configuration. Sixty-eight consecutive patients (47 men, mean age, 72.8±9.8years) who underwent TEVAR with proximal fixation in zones 1 to 3 from March 2009 to February 2017 were included. Preoperative and postoperative computed tomography (CT) scans were retrospectively reviewed. Relationships between the incidence of a bird-beak configuration, preoperative aortic arch morphology, and type of stent graft were estimated. The influence of a bird-beak configuration on endograft migration over time was also estimated for 47 patients who underwent CT 12months after TEVAR. The patients' aortic arch pathologies included 52 aneurysms, 11 aortic dissections, 4 pseudoaneurysms, and 1 patent ductus arteriosus. Stent grafts with (the proximal bare stent group [PBS group]) and without (the nonbare stent group [NBS group]) a proximal bare stent were implanted in 24 and 44 patients, respectively. A bird-beak configuration was detected in 30 patients (mean length ± standard deviation [SD], 6.2±3.4mm; mean angle ± SD, 31.7±14.7°) and was significantly more frequent in the NBS group (n=29) than in the PBS group (n=1) (P<0.001). Proximal landing zone, aortic lengths, and aortic arch morphology, including the radius, tortuosity, and angulation of aortic arch curvature, were not associated with the bird-beak configuration. The migration distance after 1year was significantly longer in patients with a bird-beak configuration (3.5±6.1mm) than in patients without a bird-beak configuration (0.5±1.0mm) (P=0.015). This study demonstrated that in aortic arch TEVAR, the use of stent graft with a proximal bare stent may reduce bird-beak configuration, which is associated with distal migration of the stent graft during follow-up.