Background: Coronary heart disease is a leading cause of mortality among women. Systematic evaluation of the quality of care and outcomes in women hospitalized for acute coronary syndrome (ACS), an acute manifestation of coronary heart disease, remains lacking in China. Methods: The CCC-ACS project (Improving Care for Cardiovascular Disease in China–Acute Coronary Syndrome) is an ongoing nationwide registry of the American Heart Association and the Chinese Society of Cardiology. Using data from the CCC-ACS project, we evaluated sex differences in acute management, medical therapies for secondary prevention, and in-hospital mortality in 82 196 patients admitted for ACS at 192 hospitals in China from 2014 to 2018. Results: Women with ACS were older than men (69.0 versus 61.1 years, P <0.001) and had more comorbidities. After multivariable adjustment, eligible women were less likely to receive evidence-based acute treatments for ACS than men, including early dual antiplatelet therapy, heparins during hospitalization, and reperfusion therapy for ST-segment–elevation myocardial infarction. With respect to strategies for secondary prevention, eligible women were less likely to receive dual antiplatelet therapy, angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, statins at discharge, and smoking cessation and cardiac rehabilitation counseling during hospitalization. In-hospital mortality rate was higher in women than in men (2.60% versus 1.50%, P <0.001). The sex difference in in-hospital mortality was no longer observed in patients with ST-segment–elevation myocardial infarction (adjusted odds ratio, 1.18; 95% CI, 1.00 to 1.41; P =0.057) and non-ST–segment elevation ACS (adjusted odds ratio, 0.84; 95% CI, 0.66 to 1.06; P =0.147) after adjustment for clinical characteristics and acute treatments. Conclusions: Women hospitalized for ACS in China received acute treatments and strategies for secondary prevention less frequently than men. The observed sex differences in in-hospital mortality were mainly attributable to worse clinical profiles and fewer evidence-based acute treatments provided to women with ACS. Specially targeted quality improvement programs may be warranted to narrow sex-related disparities in quality of care and outcomes in patients with ACS. Clinical Trial Registration: URL: https://www.clinicaltrials.gov . Unique identifier: NCT02306616.