The objective of this study was to report the short- and medium-term outcome of surgeon-modified fenestrated endovascular aneurysm repair (SM-FEVAR) for acute complex aortic aneurysms. Interrogation of a prospectively maintained database identified consecutive patients who underwent SM-FEVAR for acute complex aortic aneurysms (including mycotic aneurysms treated with rifampicin-soaked endografts) in a single institution between October 2009 and November 2018. A total of 54 patients (37 men; median age, 73 years [range, 50-85 years]; aneurysm diameter, 76 mm [interquartile range, 58-90 mm]) with acute thoracoabdominal aortic aneurysms (n = 50; 40 symptomatic, 10 ruptured; 19 extent I-III, 31 extent IV) or symptomatic type IA endoleaks after infrarenal endovascular aneurysm repair (n = 4) underwent SM-FEVAR. Seven of the patients had adjunct chimney and periscope stent grafts or surgical bypasses. A total of 187 vessels (mean, 3.4 [range, 1-5] per patient) were targeted for preservation; nine occluded intraoperatively or within 30 days. The 30-day/in-hospital mortality was 16.7% (n = 9; symptomatic, 7.4%; rupture, 50%) and fell significantly from 29.6% (n = 8) in the first 27 patients to 3.7% (n = 1) in the most recent 27 patients (P = .0243). Spinal cord ischemia occurred in one patient (1.9%) who died within 30 days. No survivors required permanent renal dialysis. Estimated survival at 12 and 24 months was 73.2% (standard error [SE], 6.2%). Eight patients underwent 12 late aorta- or graft-related reinterventions. Estimated freedom from reintervention at 12 months and 24 months was 87.9% (SE, 5.2%) and 81.6% (SE, 6.4%), respectively. In patients with acute complex aneurysms, SM-FEVAR provides a customized solution that is associated with good medium-term survival and durability. The knowledge and skills to perform safe SM-FEVAR should be within the capabilities of high-volume specialist aortic centers. Copyright © 2019 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.