Objective: We report a child presenting with spinal myelopathy secondary to H3K27M mutant diffuse midline glioma. Case Report: A 4-year-old boy presented with a 3-week history of progressive gait difficulty. Examination revealed bilateral hand and lower extremity weakness, left leg hypertonia with ankle clonus, and a right hemisensory deficit. Magnetic resonance imaging of neuroaxis showed cervical and thoracic spinal cord with expansion and irregular areas of enhancement. Serum and cerebrospinal fluid studies were unremarkable for infectious, autoimmune, inflammatory, and neoplastic causes but showed mild cerebrospinal fluid pleocytosis, hypoglycorrhachia, and high protein level. A thoracic cord biopsy revealed a diffuse midline glioma (World Health Organization grade IV). Consequently, the tumor involved intracranial structures and patient died within 4 months after diagnosis. Conclusion: High-grade spinal cord gliomas are very rare but should be considered in the differential diagnosis of pediatric myelopathy. Tissue biopsy is recommended in indeterminate cases to facilitate diagnosis and to guide management.