Invasive aspergillosis in hematologic pediatric patients is an opportunistic infection that is difficult to treat, with a high mortality rate when localized in the central nervous system. We are describing a 3-year-old girl who was affected by acute lymphoblastic leukemia who developed cerebral and pulmonary aspergillosis during induction chemotherapy. The patient failed first-line voriconazole treatment because of being a CYP2C19 ultrarapid metabolizer and received effective isavuconazole therapy with no notable side effects.