Background: We sought to explore the relationship between dexmedetomidine as an anesthetic adjuvant in cardiac surgery and postoperative complications and length of stay (LOS) in the cardiac intensive care unit (CICU). Methods: We conducted a retrospective study of patients aged 18 years and older who underwent heart valve surgery between October 2020 and June 2022. The study endpoints were a combination of adverse outcomes, which included major postoperative complications (cardiac arrest, atrial fibrillation, myocardial injury/infarction, heart failure) and prolonged CICU LOS (defined as LOS≥90th percentile). Multivariate logistic regression analysis was performed for variables that were significant in the univariate analysis. Results: A total of 856 patients entered our study. Of these, 283（33.06%） patients experienced at least one adverse outcome and the remaining 573 were included in the prognostic control group. Multivariate logistic regression analysis revealed that age > 60years (odds ratio [OR], 1.73; 95% confidence interval [CI], 1.27–2.37; p=0.01), cardiopulmonary bypass( CPB)> 190min (OR, 1.58; 95% CI, 1.01-2.48; p = 0.04) and postoperative mechanical ventilation time > 10 h (OR, 2.03; 95% CI, 1.49-2.77; p < 0.01) were independent risk factors for major complications and prolonged CICU length of stay in patients undergoing heart valve surgery. Intraoperative use of dexmedetomidine as an anesthetic adjuvant was a protective factor for such patients (odds ratio, 0.53; 95% confidence interval, 0.37-0.78; p = 0.01). Conclusions: Age, duration of cardiopulmonary bypass, and duration of mechanical ventilation are associated with major complications and increased CICU stay after heart valve surgery. Intraoperative use of dexmedetomidine may improve such clinical outcomes.