BACKGROUND: There is a paucity of data regarding the safety and efficacy of different antiplatelet regimens according to standardized body mass index (BMI) categories. OBJECTIVES: The aim of this study was to investigate bleeding and ischemic outcomes according to BMI in the TWILIGHT (Ticagrelor With Aspirin or Alone in High-Risk Patients After Coronary Intervention) trial. METHODS: The TWILIGHT trial randomized high-risk patients to ticagrelor plus aspirin or ticagrelor plus placebo at 3 months after percutaneous coronary intervention. In this secondary analysis, patients were stratified by standard BMI categories, as recommended by the European Society of Cardiology Working Group on Thrombosis (normal weight [BMI 18.5-24.99 kg/m2], overweight [BMI 25-29.99 kg/m2], and obese [BMI ≥30 kg/m2]) and by median BMI, as prespecified in the protocol. RESULTS: Among 7,038 patients randomized and with available BMI, 1,807 (25.7%) were normal weight, 2,927 (41.6%) were overweight, and 2,304 (32.7%) were obese. In normal-weight, overweight, and obese patients, ticagrelor monotherapy, compared with ticagrelor plus aspirin, reduced the primary endpoint of Bleeding Academic Research Consortium type 2, 3, or 5 bleeding (normal weight: HR: 0.48 [95% CI: 0.32-0.73]; overweight: HR: 0.57 [95% CI: 0.41-0.78]; obese: HR: 0.63 [95% CI: 0.44-0.91]; P for interaction = 0.627), without any increase in the composite ischemic endpoint of all-cause death, myocardial infarction, or stroke (normal weight: HR: 1.36 [95% CI: 0.84-2.19]; overweight: HR: 0.92 [95% CI: 0.63-1.35]; obese: HR: 0.84 [95% CI: 0.56-1.25]; P for interaction = 0.290). These findings were consistent with the prespecified analysis by median BMI. CONCLUSIONS: Among high-risk patients undergoing percutaneous coronary intervention, ticagrelor monotherapy, compared with ticagrelor plus aspirin, reduced bleeding events without any increase in ischemic risk across different BMI categories.