Background: Concomitant procedures during endovascular aneurysm repair (EVAR) of an abdominal aortic aneurysm are performed to facilitate endograft delivery, to simultaneously treat unrelated conditions, or to resolve intraoperative pitfalls. The frequency and perioperative impact of these procedures are not well described. This study aimed to assess the frequency and perioperative impact of various concomitant procedures performed at the time of EVAR. Methods: We included all elective EVARs in the Vascular Study Group of New England between January 2003 and November 2014 and identified those with and those without concomitant procedures. Multivariable logistic regression analysis was used to establish the independent association between concomitant procedures and perioperative outcomes. Results: The study included 4033 patients, with 1168 (29.0%) patients undergoing one or more additional procedures. Independent risk factors for 30-day mortality were concomitant femoral endarterectomy (odds ratio [OR], 4.8; 95% confidence interval [CI], 2.1-11.2) and renal angioplasty or stenting (OR, 3.1; 95% CI, 1.2-8.3). Postoperative bowel ischemia was associated with hypogastric embolization (OR, 3.8; 95% CI, 1.1-13.4) and iliac angioplasty or stenting (OR, 3.5; 95% CI, 1.3-9.6). Leg ischemia was associated with unplanned graft extension (OR, 2.3; 95% CI, 1.02-5.0), other artery reconstruction (OR, 5.2; 95% CI, 1.8-15.1), thromboembolectomy (OR, 5.2; 95% CI, 1.3-20.8), and repair of arterial injury (OR, 4.6; 95% CI, 1.2-18.3). Risk factors for deterioration of renal function were iliofemoral bypass (OR, 3.9; 95% CI, 1.3-12.2), other artery reconstruction (OR, 2.7; 95% CI, 1.3-5.8), renal angioplasty or stenting (OR, 2.5; 95% CI, 1.3-4.6), and repair of arterial injury (OR, 4.5; 95% CI, 1.6-12.2). Myocardial infarction was associated with femorofemoral bypass (OR, 3.9; 95% CI, 1.7-8.7), other artery reconstruction (OR, 3.9; 95% CI, 1.6-9.2), and repair of arterial injury (OR, 6.1; 95% CI, 1.8-21.0). Wound complications were predicted by femorofemoral bypass (OR, 13.4; 95% CI, 5.8-31.1). Conclusions: Concomitant procedures during EVAR are associated with increased postoperative morbidity and mortality. The need for performing concomitant procedures should be carefully considered. The morbidity associated with intraoperative complications highlights the importance of avoidance of arterial injury and thromboembolic events where possible.