Background Stroke is a major comorbidity in patients with heart failure (HF), especially in those with decreased left atrial (LA) function, and thus, identifying patients highly at risk of stroke can prevent its occurrence. We evaluated the predictive value of global longitudinal strain of LA (LAGLS) in patients with acute HF and sinus rhythm. Methods and Results In this retrospective study, 2461 patients (53.3% men, 69.7±14.4 years old) with sinus rhythm and LAGLS among 4312 consecutive patients with acute HF from 3 tertiary hospitals were included. HF phenotypes were defined as HF with reduced ejection fraction (EF) (left ventricular EF ≤40%), HF with midrange EF (40% <left ventricular EF <50%), and HF with preserved ejection fraction (left ventricular EF ≥50%). Primary outcome was new-onset stroke. The mean left ventricular EF was 39.4%±15.6%. Moreover, 1388 (57.5%), 342 (14.2%), and 682 (28.3%) were classified with HF with reduced EF, HF with midrange EF, and HF with preserved EF, retrospectively. LAGLS was 17.2%±10.4%. During the follow-up duration (mean: 30.3±25.4 months), 100 patients experienced stroke. Patients with stroke had higher LA diameter (P=0.031) and lower LAGLS (P=0.010) than those without stroke. In the univariate analysis, age, diabetes mellitus, LA diameter, LA volume index, and LAGLS were significant risk factors for stroke. In the multivariate analysis, each 1% decrease in LAGLS was associated with a 3.8% increased risk for stroke (hazard ratio [HR], 1.038; 95% CI, 1.013-1.065; P=0.003). When applying a LAGLS cutoff point of 14.5%, patients with LAGLS <14.5% had approximately twice the risk for stroke after adjusting other significant variables (HR, 1.940; 95% CI, 1.269-2.965; P=0.002). Conclusions In patients with acute HF and sinus rhythm, decreased LAGLS (<14.5%) was associated with an increased risk for stroke, with an annual incidence of 2.38%.