According to the Third World Symposium on Pulmonary Arterial Hypertension (PAH), chemotherapy is considered to be one of the possible risk factors for patients developing PAH. However, to date, no literature has sufficiently addressed the risk, natural history, and effective treatment of this condition. We report our experience on how early diagnosis, detailed monitoring of disease course, and appropriate treatment application have led to a successful outcome of PAH management in childhood after cancer therapy. Our report reaffirmed the fact that PAH is now a recognized complication of chemotherapy and bone marrow transplantation for leukemia. Combined pulmonary vasodilator treatment has a beneficial effect in improving the patient’s condition and functional status as suggested by initial acute pulmonary vasodilator testing.