The available literature on morbidity risk of cardiovascular diseases associated with ambient ozone pollution is still limited. This study examined the potential acute effects of exposure to ambient ozone pollution on hospital admissions of cardiovascular events in China. A two-stage multi-city time-series study approach was used to explore the associations of exposure to ambient ozone with daily hospital admissions (n = 6 444 441) for cardiovascular events in 70 Chinese cities of prefecture-level or above during 2015–17. A 10 μg/m³ increment in 2-day average daily 8 h maximum ozone concentrations was associated with admission risk increases of 0.46% [95% confidence interval (CI): 0.28%, 0.64%] in coronary heart disease, 0.45% (95% CI: 0.13%, 0.77%) in angina pectoris, 0.75% (95% CI: 0.38%, 1.13%) in acute myocardial infarction (AMI), 0.70% (95% CI: 0.41%, 1.00%) in acute coronary syndrome, 0.50% (95% CI: 0.24%, 0.77%) in heart failure, 0.40% (95% CI: 0.23%, 0.58%) in stroke and 0.41% (95% CI: 0.22%, 0.60%) in ischemic stroke, respectively. The excess admission risks for these cardiovascular events associated with high ozone pollution days (with 2-day average 8-h maximum concentrations ≥100 µg/m³ vs. < 70 µg/m³) ranged from 3.38% (95% CI: 1.73%, 5.06%) for stroke to 6.52% (95% CI: 2.92%, 10.24%) for AMI. Ambient ozone was associated with increased hospital admission risk for cardiovascular events. Greater admission risks for cardiovascular events were observed under high ozone pollution days. These results provide evidence for the harmful cardiovascular effects of ambient ozone and call for special attention on the control of high ozone pollution. Ozone Pollution and Hospital Admissions for Cardiovascular Events