Objective: The long-term survival differences between endovascular repair (EVAR) and open repair for abdominal aortic aneurysms (AAAs) and specifically the impact of age on these differences remain a topic of debate. Therefore, we compared the long-term mortality between EVARand open abdominal aneurysm repair for patients of different ages. Methods: This was a retrospective cohort study of prospectively collected data from patients undergoing elective EVAR or open repair for infrarenal AAAs within the Vascular Quality Initiative multinational clinical registry (2003-2021). The primary outcome was long-term all-cause mortality comparing EVAR and open repair for patients aged less than 65 years, between 65 and 79 years, and those aged 80 and older. In addition, we investigated the interaction between repair modality and 10-year hazard of mortality for sex, aneurysm diameter, and several preoperative comorbid conditions within each age category. To account for the nonrandom assignment of treatment, we used propensity scores and inverse probability weighted Cox proportional hazard analysis. Results: We identified 48,074 patients undergoing elective infrarenal abdominal aneurysm repair (89% EVAR) within the study period, including 7940 patients aged less than 65, 29,555 aged between 65 and 79, and 10,579 aged 80 years or more. EVAR was associated with a higher propensity score-adjusted long-term hazard of mortality compared with open repair in the cohort aged less than 65 years (hazard ratio [HR], 1.39; 95% confidence interval [CI], 1.04-1.86; P = .026). The mortality was similar in the age cohort between 65 and 79 (HR, 0.94; 95% CI, 0.79-1.10; P = .43), whereas EVAR was associated with a lower hazard of mortality in the cohort aged 80 years or more (HR, 0.63; 95% CI, 0.46-0.86; P = .004). In patients aged less than 65 years, the hazard of mortality was higher with EVAR compared with open repair in those with female sex (HR, 4.40; 95% CI, 1.75-11.0), an aneurysm diameter of more than 65 mm (HR, 2.19; 95% CI, 1.11-4.34), and an absence of coronary artery disease (HR, 1.26; 95% CI, 0.83-1.91), congestive heart failure (HR, 1.41; 95% CI, 1.03-1.92), and renal dysfunction (HR, 1.46; 95% CI, 1.04-2.05). In the patient cohort aged 80 and older, a lower hazard of mortality for EVAR versus open repair was observed for male patients or those with small aneurysms or certain comorbidities. Conclusions: In a selected group of young patients with a substantial life expectancy, the long-term mortality is higher with EVAR compared with open repair for infrarenal AAAs. Long-term mortality with EVAR is similar in the middle cohort and lower in the elderly cohort compared with open repair.