Objective: Female sex is associated with worse outcomes after infrarenal abdominal aortic aneurysm (AAA) repair. However, the impact of female sex on complex AAA repair is poorly characterized. Therefore, we compared outcomes between female and male patients after open and endovascular treatment of complex AAA. Methods: We identified all patients who underwent complex aneurysm repair between 2011 and 2017 in the American College of Surgeons National Surgical Quality Improvement Program targeted vascular module. Complex repairs were defined as those for juxtarenal, pararenal, or suprarenal aneurysms. We compared rates of perioperative adverse events between female and male patients stratified by open AAA repair and endovascular aneurysm repair (EVAR). We calculated propensity scores and used inverse probability-weighted logistic regression to identify independent associations between female sex and our outcomes.Results: We identified 2270 complex aneurysm repairs, of which 1260 were EVARs (21.4% female) and 1010 were open repairs (30.7% female). After EVAR, female patients had higher rates of perioperative mortality (6.3% vs 2.4%; P = .001) and major complications (15.9% vs 7.6%; P < .001) compared with male patients. In contrast, after open repair, perioperative mortality was not significantly different (7.4% vs 5.6%; P = .3), and the rate of major complications was similar (29.4% vs 27.4%; P = .53) between female and male patients. Furthermore, even though perioperative mortality was significantly lower after EVAR compared with open repair for male patients (2.4% vs 5.6%; P = .001), this difference was not significant for women (6.3% vs 7.4%; P = .60). On multivariable analysis, female sex remained independently associated with higher perioperative mortality (odds ratio [OR], 2.5; 95% confidence interval [CI], 1.3-4.9; P = .007) and major complications (OR, 2.0; 95% CI, 1.3-3.2; P = .002) in patients treated with EVAR but showed no significant association with mortality (OR, 0.9; 95% CI, 0.5-1.6; P = .69) or major complications (OR, 1.1; 95% CI, 0.8-1.5; P = .74) after open repair. However, the association of female sex with higher perioperative mortality in patients undergoing complex EVAR was attenuated when diameter was replaced with aortic size index in the multivariable analysis (OR, 1.9; 95% CI, 0.9-3.9; P = .091).Conclusions: Female sex is associated with higher perioperative mortality and more major complications than for male patients after complex EVAR but not after complex open repair. Continuous efforts are warranted to improve the sex discrepancies in patients undergoing endovascular repair of complex AAA.