We aimed to investigate the association between carotid plaques and cognitive impairment among patients with acute ischemic stroke, and to assess key clinical implications. In the Acute Ischemic Stroke Study, patients who received a cognitive testing and underwent complete carotid artery ultrasound scans were included. Cognitive function was measured by the mini-mental state examination. The cross-sectional relationships between cognitive impairment and carotid plaques were evaluated using multivariate logistic regression analysis. Of the 3116 patients included in this study, 826 (26.51%) patients were diagnosed with cognitive impairment. After adjusting for potential confounders, patients with ≥2 carotid plaques (odds ratio [OR] = 1.47; 95% confidence interval [CI]: 1.19-1.82), patients with ≥2 number of carotid arteries with plaque (OR = 1.48; 95% CI: 1.19-1.84) and patients with hypoechoic plaque (OR = 2.05; 95% CI: 1.24-3.38) are more likely to have cognitive impairment. In this acute ischemic stroke population, the number of carotid plaques, the number of carotid arteries with plaque and plaque stability are all associated with cognitive impairment.