© The Author(s) 2019. Published by Oxford University Press on behalf of the European Society of Cardiology. Aims Lowering low-density lipoprotein cholesterol (LDL-C) reduces cardiovascular risk irrespective of age, but the evidence is less strong for older patients. Methods and results This prespecified analysis from ODYSSEY OUTCOMES compared the effect of alirocumab vs. placebo in 18 924 patients with recent acute coronary syndrome (ACS) according to age. We examined the effect of assigned treatment on occurrence of the primary study outcome, a composite of coronary heart disease death, myocardial infarction, ischaemic stroke, or unstable angina requiring hospitalization [major adverse cardiovascular event (MACE)] and all-cause death. Relative risk reductions were consistent for patients >_ 65 vs. <65 years for MACE [hazard ratio (HR) 0.78, 95% confidence interval (CI) 0.68-0.91 vs. 0.89, 0.80-1.00; Pinteraction = 0.19] and all-cause death [HR 0.77, 0.62-0.95 vs. 0.94, 0.77-1.15; Pinteraction = 0.46], and consistent for MACE when dichotomizing at age 75 years (HR 0.85, 0.64-1.13 in >_ 75 vs. 0.85, 0.78-0.93 in <75, Pinteraction = 0.19). When considering age as a continuous variable in regression models, advancing age increased risk of MACE, as well as the absolute reduction in MACE with alirocumab, with numbers-needed-to-treat for MACE at 3 years of 43 (25-186) at age 45 years, 26 (15-97) at age 75 years, and 12 (6-81) for those at age 85 years. Although adverse events were more frequent in older patients, there were no differences between alirocumab and placebo. Conclusion In patients with recent ACS, alirocumab improves outcomes irrespective of age. Increasing absolute benefit but not harm with advancing age suggests that LDL-C lowering is an important preventive intervention for older patients after ACS.