This study was conducted to evaluate the prognostic value of the frailty index based on routine laboratory data (FI-L) in elderly patients who underwent surgical aortic valve replacement (SAVR). A total of 154 elderly patients (≥ 75 years) (78.7 ± 3.6 years; men:women = 78:76) who underwent aortic valve replacement with stented bioprosthesis between 2001 and 2018 were enrolled. The FI-L was calculated as the proportion of abnormal results out of 32 items based on laboratory tests, pulse rate and blood pressure. The primary outcome was all-cause mortality. Secondary outcomes included operative mortality and aortic valve-related events (AVREs) during follow-up. The predictive values of FI-L for the early and late outcomes were evaluated using logistic regression and Cox proportional hazards models, respectively. The median follow-up duration was 40 months (interquartile, 15-74). The operative mortality rate was 3.9% (n = 6). Late death occurred in 29 patients. The overall survival (OS) rates at 5, 10, and 15 years were 83.3%, 59.0%, and 41.6%, respectively. The AVREs occurred in 28 patients and the freedom rates from AVREs at 5, 10, and 15 years were 79.4%, 72.7%, and 52.9%, respectively. Multivariable analyses demonstrated that FI-L was a significant factor for OS (hazard ratio, 1.075; 95% confidence interval, 1.040-1.111). A minimal P value approach showed that a FI-L of 25% was the best cutoff value to predict OS after SAVR. The FI-L is significantly associated with early and long-term outcomes after SAVR in elderly patients. Frailty rather than a patient's age should be considered in the decision-making process for SAVR in elderly patients. © 2019 The Korean Academy of Medical Sciences.