Background Studies demonstrate that cardiopulmonary bypass (CPB) causes intraoperative and postoperative hyperglycemia. Hyperglycemia has been associated with morbidity and mortality after infant cardiac surgery. We studied the effects on early postoperative outcomes of glucose (GLU) changes during and after pediatric cardiac surgery. Methods The records of 144 infants less than 10 kg who underwent CPB for a variety of congenital cardiac procedures were reviewed. The GLU values (at multiple intervals during and after surgery), age, weight, CPB time, ultrafiltration volume, and risk adjustment for congenital heart surgery (RACHS-1) score were recorded. Univariate and multivariate linear and binary logistic regression were used to examine the dependence of the composite outcome mortality or postoperative infection, the mechanical ventilation time (VENT time), and the length of stay (LOS), on these variables. Results The RACHS-1 score was the only significant predictor of the composite variable “mortality or infection” ( p = 0.008). Glucose at any time was not a significant factor predicting this outcome. Lower pre-CPB GLU, younger age, and higher RACHS-1 score were significant predictors of greater LOS and VENT time. Conclusions In this study, post-CPB and postoperative hyperglycemia were not risk factors for postoperative morbidity and mortality after infant cardiac surgery.