Asparaginase treatment is associated with several adverse effects, including allergy, thromboembolic events, acute pancreatitis, altered liver function, and hyperglycemia. In addition, asparaginase can cause abnormalities in lipid metabolism, predominantly hypercholesterolemia and -triglyceridemia. Herein, we report on the case of a 5-year-old male presenting with acute severe hypertriglyceridemia caused by accidental pegylated asparaginase push during treatment of relapsed acute lymphoblastic leukemia. Hypertriglyceridemia did not occur after appropriate administrations of pegylated asparaginase before and after accidental drug infusions, so we speculate that the rate of pegylated asparaginase administration may have an effect on the serum triglyceride level.