Abstract The aim of this study was to investigate the association between persistent nocturnal sleep duration patterns and carotid intima-media thickness (CIMT) in Chinese patients with type 2 diabetes mellitus (T2DM). From March 1, 2018 to August 31, 2023, a cross-sectional study was carried out at the National Metabolic Management Center of the First Affiliated Hospital of Ningbo University. Each patient completed a minimum of three sleep questionnaire assessments during the study period. Group-based trajectory modeling was employed to identify distinct groups of patients exhibiting different trajectories of nocturnal sleep duration. CIMT ≥ 1 mm was used to assess early atherosclerotic changes in arterial structure. Multiple logistic regression was used to assess the association between trajectories of nocturnal sleep duration and CIMT. Three trajectories of nocturnal sleep duration were identified: persistent short (6.44 h: n = 114, 13.5% of all subjects), persistent moderate (7.59 h: n = 500, 59.0%), and persistent long (8.69 h: n = 233, 27.5%). After adjusting for age, sex, education, body mass index, physical activity, current smoking, current alcohol drinking, hypertension, hyperlipidemia, and HbA1c, the odds of CIMT ≥ 1 mm were found to be higher in patients with persistent short nocturnal sleep duration (OR 3.03, 95%CI 1.15, 7.98). However, no significant association was found between persistent long sleep duration at night and CIMT ≥ 1 mm. Persistent short nocturnal sleep duration was associated with increased CIMT in Chinese patients with T2DM. Further longitudinal studies are warranted to fully elucidate this topic.