Purpose: Off-the-shelf and custom thoracic endovascular aortic repair (TEVAR) solutions for aortic arch and descending aortic pathologies have transformed contemporary treatment landscape. However, consideration must be given to arch and supra-aortic vessel anatomy to ensure both antegrade perfusion is maintained, as well as satisfactory proximal seal zones can be obtained. This study aims to compare left common carotid to left subclavian artery (LCCA-LSCA) transposition with conventional carotid–subclavian bypass/debranching for supra-aortic revascularisation in patients undergoing thoracic endovascular aortic repair (TEVAR). Methods and Materials: A single-centre case-control study was performed including consecutive patients undergoing TEVAR with supra-aortic reconstruction prior. Patients underwent either LCCA-LSCA transposition or conventional debranching with bypass. Primary outcomes included stroke, technical success, immediate LSCA patency, and 30-day mortality. Secondary outcomes included proximal landing zone length increase and reintervention rates. Results: 32 patients were included (Bypass/debranching n = 27; transposition n = 5). Technical success and immediate LSCA patency were achieved in 100% of cases in both groups, with no 30-day mortality. Stroke occurred in one patient (3.7%) in the bypass group and none in the transposition group. Reintervention was required in one bypass patient (3.7%) and none in the transposition cohort. Both techniques enabled equivalent proximal landing zone extension lengths to facilitate TEVAR. Conclusion: LCCA-LSCA transposition provides equivalent technical and anatomical outcomes to conventional bypass for LSCA revascularization and optimizing proximal landing zone length in TEVAR, while avoiding prosthetic graft use and additional anastomoses. It represents a safe and potentially more durable alternative in appropriately selected patients.