Mucormycosis are opportunistic infections mostly observed in immunocompromised patients. We report the case of a 13-year-old girl who suffered a systemic mucormycosis without presenting the usual risk factors. She was undergoing antineoplastic chemotherapy for advanced osteosarcoma of the femur with an uncommunicative pathologic fracture and pulmonary metastasis. Absidia corymbifera was isolated from skin lesions at the primary tumor site. She subsequently developed fungal pulmonary localizations and blood vessel thrombosis. Surgical treatment together with systemic, high doses of liposomal amphotericin B, posaconazole, and caspofungin cured the local infection and controlled systemic lesions. Unfortunately, the break in chemotherapy led to pulmonary metastasis progression.