Objective: As a vascular risk factor, carotid atherosclerosis is crucial to cognitive impairment. While carotid intima?media thickness, carotid artery plaque, and carotid stenosis can reflect carotid atherosclerosis in different stages, this review aimed to explore researches on the role of carotid intima?media thickness, carotid artery plaque, and carotid stenosis in the progress of cognitive impairment in nonstroke patients and tried to illustrate the possible mechanisms. Data Sources: We searched the PubMed database for recently published research articles up to July 2017, with the key words of carotid atherosclerosis, carotid intima?media thickness, carotid plaque, carotid stenosis, nonstroke, and cognitive impairment.Study Selection: Articles were obtained and reviewed to analyze the role of carotid atherosclerosis such as carotid intima?thickness, carotid plaque, and carotid stenosis in the progress of cognitive impairment in nonstroke patients and the possible mechanisms. Results: In recent years, most studies proved that by evaluating carotid atherosclerosis with ultrasonography, carotid atherosclerosis accounts for the development of cognitive decline in nonstroke patients. Carotid atherosclerosis not only impairs the subtle general cognitive function but also decreases the specific domains of cognitive function, such as memory, motor function, visual perception, attention, and executive function. But, it is still controversial. The possible mechanisms of cognitive impairment in nonstroke patients with carotid atherosclerosis can be classified as systemic global cerebrovascular function, small?vessel diseases, and the mixed lesions. Conclusions: Carotid atherosclerosis can be used to predict the risk of cognitive impairment. Furthermore, diagnosing and treating carotid atherosclerosis at early stage might help clinicians prevent and treat vascular cognitive impairment in nonstroke patients.