This study aimed to determine the prevalence of hyperglycemia among pediatric postoperative cardiac patients, its impact on outcomes, and whether hyperglycemia can be controlled effectively in this population. A retrospective chart review of 100 postoperative patients admitted to the authors’ pediatric cardiac intensive care unit (ICU) was conducted. Patients were evaluated for incidence of hyperglycemia, defined as blood glucose (BG) level exceeding 7.7 mmol/l (140 mg/dl), and outcomes. The evaluation also included 20 different postoperative patients with a BG level exceeding 7.7 mmol/l (140 mg/dl) who received management with insulin via the authors’ pediatric-specific glycemic control protocol. The BG control and hypoglycemic rates in this cohort were assessed. The prevalence of hyperglycemia was 84%. The hyperglycemic patients had higher inotrope scores, longer hospital stays, more mechanical ventilation days, and higher mortality rates than those without hyperglycemia. For the patients with hyperglycemia managed via the authors’ pediatric-specific glycemic control protocol, 62% of all BG values were within the authors’ goal range, and less than 4% of BG values were less than 3.3 mmol/l (60 mg/dl). No patient had a BG level lower than 2.2 mmol/l (40 mg/dl) during glycemic management. Severe hyperglycemia is prevalent among postoperative pediatric cardiac patients and correlates with morbidity and mortality. Hyperglycemia may be controlled effectively in these patients using a pediatric-specific glycemic control protocol without increasing the incidence of hypoglycemia.