Here, we report a case of massive rhabdomyolysis following an uncomplicated repair of a ventricular septal defect in a five-month-old baby. Postoperatively, the patient was hemodynamically stable but metabolic acidosis continued, accompanied by fever and delayed mental recovery. The next day, he became comatose and never regained consciousness thereafter. The computed tomography of the brain revealed a diffuse brain injury. The patient followed a downhill course and eventually died on postoperative day 33. An unusually high level of creatine phosphokinase was noticed, peaking (21,880 IU/L) on postoperative day 2, suggesting severe rhabdomyolysis. The relevant literature was reviewed, and the possibility of malignant hyperthermia obscured by cardiopulmonary bypass and hypothermia was addressed.