Background: Prescribing of guideline-recommended medications has been shown to reduce major adverse outcomes of patients after acute coronary syndrome. Adherence to evidence-based therapies has become a crucial element in the path to improve prognosis, especially in elderly patients with multiple comorbidities. This study aims to (1) determine the prevalence of adherence guideline-recommended medications in acute coronary syndrome elderly patients at 6-month after discharge. identify factors associated with non-adherence and the prevalence of adverse cardiovascular events. Methods: A cross-sectional and longitudinal study was conducted in all patients 60 years of age or older with acute coronary syndrome discharge from the Interventional Cardiology Department at Thong Nhat hospital from June 2020 to June 2021. Eligible patients receiving guideline - recommended medications were followed up at least 6 months in Outpatients Department. Results: There were 303 patients ≥ 60 years old diagnosed with acute coronary syndrome discharged from the hospital. The prevalence of adherence of 5 classes guideline - recommended drugs in the first month after discharge was 46.2% at the first month and decreased at 3 months to 37.3% and 33.3% at 6 months. Of those patients, P2Y12 inhibitors and statins had the highest adherence prevalence of 86.5% and 87.8%, respectively. Aspirin was 72.6%, beta blockers were 53.5% and ACE inhibitors/ angiotensin II receptor antagonists were 68%. Factors that reduced adherence to drug therapy include age, non - ST segment elevation myocardial infarction, frailty and awareness of medication duration. All-cause mortality and re - hospitalization rates were 35.3% and the non-adherence group was significantly higher with p <
0.001 (CI 0.2 - 0.55). Conclusions: The prevalence of adherence to recommended drug therapy after acute coronary syndrome in elderly patients was not high, with 46.2% at 1 month after discharge and 33.3% at 6 months. Non-adherence increased adverse cardiovascular events.