A 3-year-old male who presented with hydrocephalus symptoms was found to have metastatic medulloblastoma with diffuse spinal disease. Thirteen days following surgical resection of his primary tumor, he clinically deteriorated due to worsening brainstem edema. Following intubation, stress-dose steroids, and mannitol, urgent radiotherapy was initiated to the whole brain and cervical cord. The patient improved clinically with a repeat MRI showing decreased leptomeningeal enhancement in the radiation fields. In the literature, there are no reports of successful urgent radiotherapy in medulloblastoma, but in this instance, it proved to be a viable option.