Background: Advancing age is associated with a greater prevalence of coronary artery disease in heart failure with reduced ejection fraction and with a higher risk of complications after coronary artery bypass grafting (CABG). Whether the efficacy of CABG compared with medical therapy (MED) in patients with heart failure caused by ischemic cardiomyopathy is the same in patients of different ages is unknown. Methods: A total of 1212 patients (median follow-up, 9.8 years) with ejection fraction ≤35% and coronary disease amenable to CABG were randomized to CABG or MED in the STICH trial (Surgical Treatment for Ischemic Heart Failure). Results: Mean age at trial entry was 60 years; 12% were women; 36% were nonwhite; and the baseline ejection fraction was 28%. For the present analyses, patients were categorized by age quartiles: quartile 1, ≤54 years; quartile, 2 >54 and ≤60 years; quartile 3, >60 and ≤67 years; and quartile 4, >67 years. Older versus younger patients had more comorbidities. All-cause mortality was higher in older compared with younger patients assigned to MED (79% versus 60% for quartiles 4 and 1, respectively; log-rank P =0.005) and CABG (68% versus 48% for quartiles 4 and 1, respectively; log-rank P <0.001). In contrast, cardiovascular mortality was not statistically significantly different across the spectrum of age in the MED group (53% versus 49% for quartiles 4 and 1, respectively; log-rank P =0.388) or CABG group (39% versus 35% for quartiles 4 and 1, respectively; log-rank P =0.103). Cardiovascular deaths accounted for a greater proportion of deaths in the youngest versus oldest quartile (79% versus 62%). The effect of CABG versus MED on all-cause mortality tended to diminish with increasing age ( P _interaction =0.062), whereas the benefit of CABG on cardiovascular mortality was consistent over all ages ( P _interaction =0.307). There was a greater reduction in all-cause mortality or cardiovascular hospitalization with CABG versus MED in younger compared with older patients ( P _interaction =0.004). In the CABG group, cardiopulmonary bypass time or days in intensive care did not differ for older versus younger patients. Conclusions: CABG added to MED has a more substantial benefit on all-cause mortality and the combination of all-cause mortality and cardiovascular hospitalization in younger compared with older patients. CABG added to MED has a consistent beneficial effect on cardiovascular mortality regardless of age. Clinical Trial Registration: URL: http://www.clinicaltrials.gov . Unique identifier: NCT00023595.