Elevated red blood cell distribution width (RDW) is associated with increased risk for major adverse cardiovascular events (MACE) and death in patients with cardiovascular disease. The ODYSSEY OUTCOMES trial compared alirocumab with placebo in 18,924 patients with recent acute coronary syndrome (ACS) and elevated atherogenic lipoproteins despite optimized statin treatment. This post hoc analysis determined whether RDW independently predicts risk of MACE and death in patients after recent ACS, whether RDW influences MACE reduction with alirocumab, and whether alirocumab treatment affects RDW. Associations of baseline RDW with risk of MACE and death were analyzed in the placebo group in adjusted proportional hazards models. Interactions of RDW and treatment on the risk of MACE and death were evaluated. An increasing quartile of RDW was associated with characteristics that predicted risk of MACE and death including age, hypertension, diabetes, atherosclerotic conditions and events, revascularizations, low-density lipoprotein cholesterol, and high-sensitivity C-reactive protein. After adjusting for baseline characteristics associated with the risk of MACE or death, baseline RDW remained independently associated with the risk of MACE and death in the placebo group (hazard ratios [95% confidence intervals] 1.08 [1.02–1.15] and 1.13 [1.03–1.24] per 1% increase of RDW, respectively, both p <0.001). There was no interaction of RDW and treatment on MACE or death, nor did alirocumab affect RDW. RDW was associated with an increased risk of MACE and death, independent of established risk factors.