Objective To explore abnormal Montreal cognitive assessment (MoCA) scores in the elderly patients with carotid plaques and stenosis and to analyze the risk factors of mild cognitive impairment (MCI) in this population. Methods A retrospective analysis was made of 337 patients with carotid plaque and stenosis in the Health Management Center of First Affiliated Hospital of Soochow University from March 2021 to March 2022. They were investigated using personal information questionnaire (PIQ), MoCA scale, and mini-mental state examination (MMSE). According to MoCA scores, the patients were divided into normal cognitive function group (n=173) and MCI group (n=164). SPSS statistics 24.0 was used for data analysis. According to the data type, the t test, χ² test or Fisher′s exact probability test was used for comparison between groups. Binomial logistic regression was used to analyze the risk factors of MCI. Results The rate of MCI in the elderly patients with carotid plaque and stenosis was 48.66% (164/337), the rate of left carotid artery stenosis (56.38%) being higher than that of right carotid artery stenosis (39.17%), and the difference had statistical significance (P<0.05). Binary logistic regression analysis showed that education years (OR=0.595,95%CI 0.453-0.782; P<0.001) and albumin (OR=0.153,95%CI 0.033-0.712; P=0.017) were the protective factors in MCI patients and that the average daily sleep time <8h in the last month (OR=2.532,95%CI 1.655-3.932; P=0.025), duration of hypertension (OR=1.221,95%CI 1.029-1.448; P=0.022), body mass index (BMI) (OR=1.112,95%CI 1.021-1.535; P=0.012), platelet count (OR=1.032,95%CI 1.002-1.062; P=0.036), monocyte count (OR=1.186,95%CI 1.052-1.338; P=0.012), and glycosylated hemoglobin (OR=2.205,95%CI 1.291-4.470; P=0.015) were risk factors. Conclusion Patients with left carotid plaque and stenosis had a higher risk of MCI than those with right carotid plaque and stenosis. The average daily sleep time <8h in the last month, duration of hypertension, BMI, platelet count, monocyte count and glycosylated hemoglobin were risk factors for MCI in the elderly patients with carotid artery stenosis.