Acute lymphoblastic leukemia (ALL) is the most common pediatric hematologic malignancy. Exposure to certain cytotoxic therapies for ALL is associated with an increased risk of secondary malignancies.We present a rare case of a 6-year-old girl with secondary acute myeloid leukemia (AML) that occurred while the patient was receiving maintenance therapy for ALL approximately 17 months from the time of primary diagnosis. This case indicates that if pediatric patients with ALL receive induction chemotherapy agents used for adults, such as idarubicin and cyclophosphamide, they may have a shorter time to the progression of secondary malignancies.