OBJECTIVE Vancomycin is often used in the pediatric cardiac surgical population, but few pharmacokinetic data are available to guide dosing. METHODS A retrospective, population pharmacokinetic study was performed for patients <19 years of age initiated on vancomycin after cardiac surgery in the cardiac intensive care unit from 2011-2016 in our institution. Patient data were summarized by using descriptive statistical methods, and population pharmacokinetic analysis was performed by using NONMEM. Simulation was performed to determine a dosing strategy that most frequently obtained an AUC0-24:MIC (minimum inhibitory concentration) ratio of >400. RESULTS A total of 261 patients (281 cardiac surgical procedures, cardiopulmonary bypass 82.3%) met inclusion criteria (60.1% male, median age 0.31 [IQR, 0.07-0.77] years). Vancomycin (14.5 ± 1.7 mg/kg/dose) was administered at median postoperative day 9 (IQR, 4-14), with a mean serum concentration of 11.5 ± 5.5 mg/L at 8.9 ± 3.8 hours after a dose. Population pharmacokinetic analysis demonstrated that a 1-compartment proportional error model with allometrically scaled weight best fit the data, with creatinine clearance and postmenstrual age as significant covariates. Simulation identified that a dosing regimen of 20 mg/kg/dose every 8 hours was most likely to achieve an AUC0-24:MIC ratio > 400 at a mean trough serum concentration of 12.9 ± 3.2 mg/L. CONCLUSIONS Vancomycin dosing in the postoperative pediatric cardiac surgical population should incorporate postmenstrual age and creatinine clearance. A vancomycin dose of 20 mg/kg every 8 hours is a reasonable empiric strategy.