Purpose Although left atrial (LA) expansion index predicts cardiovascular events, its efficacy for predicting cerebral events is unknown. Methods This study enrolled 2205 patients who had sinus rhythm after echocardiography in their first visit. LA expansion index was calculated as (Vol(max)-Vol(min)) x100%/Vol(min), where Vol(max) was defined as maximal LA volume and Vol(min) as minimal LA volume. The study endpoint was ischemic stroke. Stroke subtype was classified as cardioembolic stroke (CE), noncardioembolic stroke with determined mechanism (NCE), or embolic stroke of undetermined source (ESUS). Results Over a 10-year (mean 9.7 years) follow-up period, 128 (5.8%) participants reached endpoint, including 46 with CE, 33 with NCE, and 49 with ESUS. Regardless of stroke subtype, LA expansion index was lower in the event groups compared to the nonevent group. The lowest quartile of LA expansion index was associated with high CHA(2)DS(2)-VASc score at enrollment and more events, including CE, ESUS, atrial fibrillation (AF), heart failure, and all-cause mortality, relative to other quartiles. The LA expansion index was an independent predictor of CE (HR 0.82; 95% CI 0.723-0.912, per 10% increase in LA expansion index; P < .0001) and ESUS (HR 0.92; 95% CI 0.881-0.976, per 10% increase in LA expansion index; p 0.003). An LA expansion index <68% predicts the presence of AF after ESUS with 84% sensitivity and 70% specificity. Conclusion LA expansion index is useful for predicting CE and ESUS. It is also associated with AF, heart failure hospitalization, and all-cause mortality.