Background Stroke incidence is elevated after acute coronary syndromes (ACS). The aim of this study was to characterize risk factors related to ischemic stroke (IS) after ACS. Methods and Results We conducted a retrospective registry study based on the data of 8049 consecutive patients treated for ACS between 2007 and 2018 in Tays Heart Hospital with a follow-up until December 31, 2020. Potential risk factors were identified by in-depth review of written hospital records and causes-of-death registry data maintained by Statistics Finland. The association between individual risk factors, early-onset IS (0-30 days after ACS, n=82), and late-onset IS (31 days to 14 years after ACS, n=419) were analyzed using logistic regression and subdistribution hazard analysis. In multivariable analysis, the most substantial risk factors for early- and late-onset IS were previous stroke, atrial fibrillation or flutter, and heart failure status depicted by the Killip classification. Left ventricular ejection fraction and coronary artery disease severity were significant risk factors for early-onset IS; age and peripheral artery disease were significant risk factors for late-onset IS. The risk of early-onset IS with ≥6 CHA2DS2-VASc score points (odds ratio, 6.63 [95% Cl, 3.63-12.09]; P<0.001) was notable compared with patients with 1 to 3 points as well as the risk of late-onset IS with ≥6 points (subdistribution hazard, 6.03 [95% Cl, 3.71-9.81]; P<0.001) in comparison with patients with 1 point. Conclusions Factors related to high thromboembolic risk also predict IS risk after ACS. CHA2DS2-VASc score and its individual components are strong predictors for both early- and late-onset IS.