BACKGROUND: Cardiac rehabilitation after an acute coronary syndrome is recommended to decrease patient morbidity and mortality and to improve quality of life. AIMS: To describe time trends in the rates of patients undergoing cardiac rehabilitation after an acute coronary syndrome in France from 2009 to 2021, and to identify possible disparities. METHODS: All patients hospitalized for acute coronary syndrome in France between January 2009 and June 2021 were identified from the national health insurance database. Cardiac rehabilitation attendance was identified within 6 months of acute coronary syndrome hospital discharge. Age-standardized cardiac rehabilitation rates were computed and stratified for sex and acute coronary syndrome subtypes (ST-segment elevation and non-ST-segment elevation). Patient characteristics and outcomes were described and compared. Factors independently associated with cardiac rehabilitation attendance were identified. RESULTS: In 2019, among 134,846 patients with an acute coronary syndrome, 22.3% underwent cardiac rehabilitation within 6 months of acute coronary syndrome hospital discharge. The mean age of patients receiving cardiac rehabilitation was 62 years. The median delay between acute coronary syndrome hospitalization and cardiac rehabilitation was 32 days, with about 60% receiving outpatient cardiac rehabilitation. Factors significantly associated with higher cardiac rehabilitation rates were male sex, younger age (35-64 years), least socially disadvantaged group, ST-segment elevation, percutaneous coronary intervention and coronary artery bypass graft. Between 2009 and 2019, cardiac rehabilitation rates increased by 40% from 15.9% to 22.3%. Despite greater upward trends in women, their cardiac rehabilitation rate was significantly lower than that for men (14.8% vs. 25.8%). In 2020, cardiac rehabilitation attendance dropped because of the coronavirus disease 2019 pandemic. CONCLUSIONS: Despite the health benefits of cardiac rehabilitation, current cardiac rehabilitation attendance after acute coronary syndrome remains insufficient in France, particularly among the elderly, women and socially disadvantaged people.