Background: Endovascular repair of complex abdominal aortic aneurysms has become increasingly common, but reports have mostly been limited to single centers and single devices. Methods: We studied all endovascular repairs of complex abdominal aortic aneurysms (zone 6 or caudal) from 2014 to 2018 in the Vascular Quality Initiative. This included all commercially available fenestrated endovascular aneurysm repair (FEVAR), chimney/snorkel repairs, and physician-modified endografts (PMEGs), exclusive of investigational device exemptions and clinical trial devices. We used inverse probability-weighted multilevel logistic regression to compare rates of perioperative outcomes including death, acute kidney injury (AKI), and major adverse cardiac events (MACEs; the composite of death/stroke/myocardial infarction) and Cox regression for long-term mortality. Results: During the study period, surgeons performed 1396 complex endovascular repairs: 1308 (94%) elective, 63 (4.5%) for symptomatic aneurysms, and 25 (1.8%) for rupture. The number of centers performing complex endovascular repairs expanded steadily from 39 in 2014 to 81 in 2017. There were 880 FEVAR (63%), 256 PMEG (18%), and 260 chimney/snorkel repairs (19%). In elective cases, 3214 visceral vessels were incorporated and revascularized; 120 repairs (9%) involved one vessel, 481 (38%) repairs involved two vessels, 560 (44%) involved three vessels, and 113 (9%) involved four vessels. The mean number of arteries incorporated was 2.5 ± 0.8, with PMEGs involving the most arteries (3.3 ± 0.8 for PMEG vs 2.5 ± 0.6 for FEVAR and 1.9 ± 0.9 for chimney/snorkel; P <.001). PMEGs were used to treat more extensive aneurysms, and more incorporated the celiac and superior mesenteric arteries. There was no change in aneurysm extent, but the length of proximal seal extended over time. Chimney/snorkel cases employed more arm or neck access, had longer procedure times, and used more contrast material. Rates of perioperative death (3.4% for FEVAR vs 2.7% for PMEG vs 6.1% for chimney/snorkel; P =.13) and AKI (17% vs 18% vs 19%; P =.42) were similar, but chimney/snorkel was associated with higher rates of stroke (0.8% vs 0.9% vs 3.3%; P =.03) and MACEs (6.1% vs 5.4% vs 11.7%; P =.02). After adjustment, rates of perioperative death, AKI, and overall complications remained similar, but chimney/snorkel was associated with significantly higher odds of stroke (odds ratio [OR], 7.3 [1.5-36.4]; P =.015), myocardial infarction (OR, 18.7 [2.6-136.8]; P =.004), and MACEs (OR, 11.1 [2.1-58.9]; P =.005). Overall survival after elective repair was 91% at 1 year and 88% at 3 years, with no difference between repair types in crude or adjusted analysis. Conclusions: The Vascular Quality Initiative provides a unique opportunity to study the real-world application and outcomes of complex endovascular aneurysm repair. Perioperative morbidity appears to be higher after chimney/snorkel repair, but further study is needed to confirm these findings and to establish the durability of these novel technologies.