Li-Fraumeni syndrome (LFS) is a cancer predisposition syndrome caused by germline TP53 mutation. Malignancies associated with LFS include osteosarcomas, leukemias, CNS, and adrenocortical tumors. While CNS tumors are common primary malignancies, we report the case of a pediatric patient with LFS who developed a never reported secondary anaplastic medulloblastoma.