Perioperative excessive blood loss (PEBL) and blood product transfusion increase morbidity and mortality in pediatric congenital heart disease patients undergoing surgerywith cardiopulmonary bypass (CPB). It is important to detect CPB-related coagulopathy earlier to be able to initiate preventive or treatment strategies to minimize perioperative blood loss and transfusion requirements in pediatric cardiac surgery. Rotational thromboelastometry (ROTEM) and conventional laboratory hemostatic variables detect the possible mechanisms of coagulopathy. Intraoperative ROTEM is useful in determining the functions of fibrinogen and platelets and thus reducing transfusion requirements in cardiac surgery. A retrospective analysis of 119 children younger than 10 years undergoing surgery for congenital heart diseasewith CPBwas done to compare the ability of laboratory hemostatic variables andROTEM parameters to predict massive perioperative surgical bleeding. Patient demographics and surgery-related clinical parameters between patients with and without PEBL were compared, and it was found that patients with PEBL showed different post-CPB ROTEM profiles and hemostatic variables from those without PEBL. This study showed that there was no significant correlation between PEBL and preoperative ROTEM or laboratory hemostatic variables. Risk factors for PEBL as shown by univariate and multivariate analyses were CPB time of more than 120 minutes (odds ratio [OR], 8.8; 95% confidence interval [CI], 2.0–39.2; P = 0.004), small post-CPB FIFTEM-A10 of less than 5 mm (OR, 11.1, 95% CI, 2.6–47.3;P< 0.001), small post-CPBEXTEM-A10 of less than 30 mm (OR, 8.4, 95% CI, 1.8–39.1; P = 0.007), and large postCPB EXTEM maximal lysis of more than 20% (OR, 6.5, 95% CI, 1.3–32.3; P = 0.022). Conventional laboratory hemostatic variables were not found to be significant predictors of PEBL. In conclusion, this analysis suggested that intraoperative ROTEM may be more useful for predicting PEBL as opposed to the laboratory hemostatic variables. Appropriate and timely transfusion and antifibrinolytic therapy guided by ROTEM can reduce perioperative blood loss in pediatric patients undergoing congenital cardiac surgery.