Hemostatic disturbances after cardiac surgery can lead to excessive postoperative bleeding. Thromboelastography (TEG) was employed to evaluate perioperative coagulative alterations in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB), investigating the correlation between factors concomitant with cardiac surgery and modifications in coagulation. Coagulation index as determined by TEG correlated significantly with postoperative bleeding at 24-72 h after cardiac surgery (P < .001). Among patients with a normal preoperative coagulation index, those with postoperative hypocoagulability showed significantly lower nadir temperature (P  =  .003), larger infused fluid volume (P  =  .003), and longer CPB duration (P  =  .033) than those with normal coagulation index. Multivariate logistic regression showed that nadir intraoperative temperature was an independent predictor of postoperative hypocoagulability (adjusted OR: 0.772, 95% CI: 0.624-0.954, P  =  .017). Multivariate linear regression demonstrated linear associations of nadir intraoperative temperature (P  =  .017) and infused fluid volume (P  =  .005) with change in coagulation index as a result of cardiac surgery. Patients are susceptible to hypocoagulability after cardiac surgery, which can lead to increased postoperative bleeding. Ensuring appropriate temperature and fluid volume during cardiac surgery involving CPB may reduce risk of postoperative hypocoagulability and bleeding.