Elderly patients are at increased risk of hemorrhagic and thrombotic complications after an acute coronary syndrome (ACS). Frailty, comorbidities and low body weight have emerged as conditioning the prognostic impact of dual antiplatelet therapy (DAPT). The aim of the present study was to investigate the prognostic impact of body mass index (BMI) on clinical outcome among patients included in the Elderly-ACS 2 trial, a randomized, open-label, blinded endpoint study comparing low-dose (5 mg) prasugrel vs clopidogrel among elderly patients with ACS. Our population is represented by 1408 patients enrolled in the Elderly-ACS 2 trial. BMI was calculated at admission. The primary endpoint of this analysis was cardiovascular (CV) mortality. Secondary endpoints were all-cause death, recurrent MI, Bleeding Academic Research Consortium (BARC) type 2 or 3 bleeding, and re-hospitalization for cardiovascular reasons or stent thrombosis within 12 months after index admission. Patients were grouped according to median values of BMI (<or ≥ 25.7 kg/m2). BMI was associated with hypertension, diabetes, hypercholesterolemia, estimated glomerular filtration rate and hemoglobin (p < 0.001), and inversely with age (p = 0.005). Overweight patients displayed larger use of diuretics at admission (p = 0.03), aspirin pre-randomization (p = 0.01) and radial access (p = 0.04). At a median follow-up of 367 [337-378] days, BMI did not affect CV mortality in the overall population 4% vs 3.8%; adjusted HR [95%CI] = 2.3 [0.8-6.5], p = 0.12. Similar findings were observed for our secondary efficacy and safety endpoints. Results did not change when considering separately higher risk subsets of patients, (female gender, diabetics, ST-segment elevation myocardial infarction or the type of DAPT treatment allocation), with no significant interaction between these population characteristics and BMI. Among elderly patients with ACS, BMI did not condition the survival or the risk of major cardiovascular and bleeding complications. The results were consistent across several patient risk categories.