Epicardial adipose tissue is involved in the pathophysiology of atrial fibrillation (AF). This study aimed to analyze its relevance as a stroke etiology marker. A retrospective study of acute ischemic stroke patients with large vessel occlusion was conducted, periatrial epicardial adipose tissue thickness (pEATT) on admission computed tomography angiography was measured. One hundred and twenty‐one patients with AF‐related stroke and 94 patients with noncardioembolic stroke were included. Patients with AF‐related stroke had increased pEATT. CT‐measured left‐sided pEATT was an independent predictor of AF‐related stroke (adjusted odds ratio per 1 mm increase = 1.27, 95% CI = 1.05–1.53, p = 0.012). pEATT is an independent marker of AF‐related stroke.