【Abstract】 Objective To explore the association between sleep disorder and prolonged ICU stay of post-cardiac surgery patients. Methods This retrospective cohort study utilized data from the Medical Information Mart for Intensive Care Ⅳ (MIMIC-Ⅳ) Database, including ICU-admitted patients who have undergone cardiac surgery between 2008 and 2019. According to the presence or absence of sleep disorders, patients were divided into normal sleep group and sleep disorder group. The association between sleep disorder and prolonged ICU stay was assessed using univariate and multivariate Logistic regression analysis. Results A total of 6,319 post-cardiac surgery patients were included in the study. The sleep disorder group exhibited a significantly higher prolonged ICU stay rate compared to the sleep normal group (31.0% vs 24.8%, P0.001). Multivariate Logistic regression analysis revealed that factors including female, age, congestive heart failure, renal disease, mean blood pressure, heart rate, mean corpuscular volume, red cell volume distribution width, blood urea nitrogen, lactate, activated partial thromboplastin time, delirium, sleep disorder independently contributed to prolonged ICU stay in post-cardiac surgery patients. Compared with the normal sleep group, the length of ICU stay was longer in the sleep disorder group, and the HR (95%CI) was 1.42 (1.03–1.96). This association remained statistically significant even after adjusting for covariates such as age, sex, ethnicity, comorbidities (HR, 1.48; 95% CI, 1.03–2.12). Conclusions Sleep disorder is a predictor of prolonged ICU stay of post-cardiac surgery patients.