Functional decrease has been linked with adverse events in different clinical contexts. The predictive role of activity of daily living status as assessed by the Barthel index (BI) in elderly patients who underwent percutaneous coronary intervention (PCI) has not been investigated, yet. In this study, a total of 616 patients (≥80 years) who underwent PCI between January 2009 and December 2014 and with available activity of daily living data on admission were stratified according to BI (low BI <85, intermediate BI 85 to 95, high BI 100). The primary end point was all-cause mortality at a total follow-up of 442 days (interquartile range 47 to 1243). Of the 616 patients, 178 (29%), 128 (21%), and 310 (50%) were in the low, the intermediate, and the high BI groups, respectively. All-cause mortality was 10%, 13%, and 5% in the low, the intermediate, and the high BI groups, respectively (log-rank p <0.001). Belonging to the high BI group was associated with a reduced risk of all-cause mortality (hazard ratio 0.35, 95% confidence interval 0.18 to 0.69, p = 0.002), and associations remained significant after multivariable adjustments (adjusted hazard ratio 0.34, 95% confidence interval 0.13 to 0.93, p = 0.04). Functional capacity was identified as independent predictor of survival in a large cohort of patients who underwent PCI. In conclusion, activities of daily living should be incorporated into the risk stratification of elderly patients with coronary artery disease.