Severe pertussis has a high mortality risk, especially in those with high white blood cell counts and pulmonary hypertension. Exchange transfusion can reduce the leukocyte mass in blood. We report 3 young infants with severe pertussis and hyperleukocytosis who developed cardiogenic shock and pulmonary hypertension. Exchange transfusion was performed. The white blood cell count decreased accompanied by improvement in the cardiopulmonary condition and survival in the 3 infants. Exchange transfusion should be considered in patients with severe pertussis with hyperleukocytosis.