The CHA₂DS₂-VASc score is a reliable tool used to estimate the risk of ischemic stroke (IS) in patients with atrial fibrillation (AF). Few tools exist for the prediction of new-onset AF (NOAF) after myocardial infarction (MI) and its relation to IS. We studied the usefulness of CHA₂DS₂-VASc in predicting NOAF and IS in a long-term follow-up after MI. Consecutive MI patients without baseline AF (n = 70,922; mean age: 68.2 years), discharged from 20 hospitals in Finland during 2005-2018, were retrospectively studied using national registries. The outcomes of interest after discharge were NOAF- and IS-assessed with competing risk analyses at one and ten years. The median follow-up was 4.2 years. The median baseline CHA₂DS₂-VASc score was 3 (IQR 2-5). The likelihood of both NOAF and NOAF-related IS increased stepwise with this score at one and ten years (all p < 0.0001). The one-year-adjusted subdistribution hazard ratio (sHR) was 4.03 (CI 3.68-4.42) for NOAF in patients with CHA₂DS₂-VASc scores ≥6 points. The cumulative incidence of IS was 15.2% in patients with NOAF vs. 6.2% in patients without AF at 10 years after MI (adj. sHR 2.12; CI 1.98-2.28; p < 0.0001). Coronary artery bypass surgery was associated with a higher NOAF incidence compared to percutaneous coronary intervention (adj. sHR 1.87; CI 1.65-2.13; p < 0.0001 one year after MI). The CHA₂DS₂-VASc score is a simple tool used to estimate the long-term risk of NOAF and IS after MI in patients without baseline AF. Coronary bypass surgery is associated with an increased NOAF incidence after MI.