Objectives Determining operative risk in patients undergoing aortic surgery is a difficult process, as multiple variables converge to affect overall mortality. Patient frailty is certainly a contributing factor, but is difficult to measure, with surgeons often relying on subjective or intuitive influences. We sought to use core muscle size as an objective measure of frailty, and determine its utility as a predictor of survival after abdominal aortic aneurysm (AAA) repair. Methods Four hundred seventy-nine patients underwent elective open AAA repair between 2000 and 2008. Two hundred sixty-two patients (54.7%) had preoperative computed tomography (CT) scans available for analysis. Cross-sectional areas of the psoas muscles at the level of the L4 vertebra were measured. The covariate-adjusted effect of psoas area on postoperative mortality was assessed using Cox regression. Results Of the 262 patients, there were 55 deaths and the mean length of follow-up was 2.3 years. Cox regression revealed a significant association between psoas area and postoperative mortality ( P = .003). The effect of psoas area was found to decrease significantly as follow-up time increased ( P = .008). Among all covariates included in the Cox models (including predictors of mortality such as American Society of Anesthesiologists ASA score), the psoas area was the most significant. Conclusion Core muscle size, an objective measure of frailty, correlates strongly with mortality after elective AAA repair. A better understanding of the role of frailty and core muscle size may aid in risk stratification and impact timing of surgical repair, especially in more complex aortic operations.