Objective: Clinical outcomes after thoracic endovascular aortic repair (TEVAR) for patients with multichanneled aortic dissection (MCAD) are poorly understood but seem substantially different from those for patients with double-channeled aortic dissection (AD). This study compared the anatomic and clinical factors for patients with MCAD who underwent TEVAR with or without full true lumen (TL) collapse.Methods: From January 2012 to March 2016, 54 of 644 consecutive type B AD patients (8.4%) who presented with MCAD were reviewed. Patients were classified as MCAD with full TL collapse and without full TL collapse according to computed tomography angiography findings. We analyzed potential variables including clinical characteristics, anatomic morphologic features, and procedural details. Multivariable analysis was performed to determine independent predictors of AD-related deaths.Results: A total of four patients (7.4%) died preoperatively of aortic rupture, all of whom experienced full TL collapse. MCAD patients with full TL collapse showed significantly higher 30-day major adverse events than those without full TL collapse (36.8% vs 9.7%; P = .030). The mean follow-up duration was 25.6 6 13.2 months (range, 3-53 months). The overall mortality for all MCAD patients was 16.7%, whereas the follow-up major adverse events rate was 40.0% after TEVAR. Significant differences were present between patients with full TL collapse and patients without full TL collapse in survival at 3 years (55.4% vs 94.7%; P = .002). Maximum diameter of affected aorta (hazard ratio, 1.176; 95% confidence interval, 1.015-1.362; P = .031) was identified as the only predictor of AD-related deaths.Conclusions: MCAD was identified in a small but not insignificant number of our patients presenting with type B AD. Urgent or elective TEVAR was indicated in all our patients with MCAD. In patients with MCAD, full TL collapse was associated with worse outcomes, and this finding may indicate the need for more urgent or emergent repair.