Background--Elderly patients with acute coronary syndrome (ACS) are at high risk for ischemic and bleeding events. This study aimed to evaluate the clinical effectiveness and safety of dual loading antiplatelet therapy for patients 75 years and older undergoing percutaneous coronary intervention for ACS. Methods and Results--The Improving Care for Cardiovascular Disease in China-ACS project was a collaborative study of the American Heart Association and Chinese Society of Cardiology. A total of 5887 patients 75 years and older with ACS who had percutaneous coronary intervention and received dual antiplatelet therapy with aspirin and P2Y12 inhibitors (clopidogrel or ticagrelor) between November 2014 and June 2017 were enrolled. The primary effectiveness and safety outcomes were in-hospital major adverse cardiovascular events and major bleeding. Hazard ratios (HRs) of in-hospital outcomes with different loading statuses of antiplatelet therapy were estimated using Cox proportional hazard models with multivariate adjustment. A propensity score-matched analysis was also conducted. Compared with patients receiving a dual nonloading dose, patients taking a dual loading dose had increased risks of both major adverse cardiovascular events (HR, 1.66, 95% confidence interval, 1.13-2.44; [P=0.010]) and major bleeding (HR, 2.34, 95% confidence interval, 1.75-3.13; [P < 0.001]). Among 3284 propensity score-matched patients, a dual loading dose was associated with a 1.36-fold risk of major adverse cardiovascular events (HR, 1.36; 95% confidence interval, 0.88-2.11 [P=0.168]) and a 2.08-fold risk of major bleeding (HR, 2.08; 95% confidence interval, 1.47-2.93 [P < 0.001]). Conclusions--A dual loading dose of antiplatelet therapy was associated with increased major bleeding risk but not with decreased major adverse cardiovascular events risk among patients 75 years and older undergoing percutaneous coronary intervention for ACS in China. © 2018 The Authors.