A 17-year-old girl with World Health Organization grade IV glioblastoma with primitive neuronal components (histone H3 G34-mutant and IDH1 wild type) underwent whole-body FDG PET/CT staging due to vertebral metastases on initial MRI. PET/CT revealed extracranial metastatic disease with spinal leptomeningeal dissemination, osseous metastases, and peritoneal seeding via a ventriculoperitoneal shunt. Glioblastoma is uncommon in pediatric patients and particularly those with primitive neuronal components. Extracranial metastases from glioblastoma are more common in those with primitive neuronal components. This case demonstrates the utility of FDG PET/CT for revealing distant metastases from glioblastoma.