Studies about continuous electrocardiographic (ECG) monitoring in detection of paroxysmal atrial fibrillation (PAF) in Asian patients with acute ischemic stroke are very limited. We looked for the prevalence and associated factors of atrial fibrillation (AF) and PAF in Thai patients with acute ischemic stroke. Methods: In all, 204 patients with acute ischemic stroke were prospectively included. Snapshot 12-lead ECG and continuous ECG monitoring for at least the first 24 hours were performed. Multivariate analyses were performed to find out the associated factors of AF and PAF. Results: AF was diagnosed in 31 patients (15%) and PAF in 15 patients (7%). Twelve and 3 patients with PAF were diagnosed by continuous ECG monitoring and snapshot 12-lead ECG, respectively. Mean duration of continuous ECG monitoring and mean time to detect PAF were 55 and 23 hours, respectively. Multivariate analysis revealed that age of 70 years or older (odds ratio [OR] 3.52, 95% confidence interval [CI] 1.68-7.35, P =.001) and heart diseases (OR 4.26, 95% CI 1.14-15.95, P =.031) were associated with AF and PAF. Conclusions: AF/PAF was one of the common causes of ischemic stroke in Thai patients. Most PAF was detected by continuous ECG monitoring. Snapshot 12-lead ECG and continuous ECG monitoring should be recommended in all patients with acute ischemic stroke. © 2014 by National Stroke Association.