Introduction: While cerebral sinovenous thrombosis (CSVT) in children is rare, the clinical manifestations can be life-threatening and cause long-term neurological deficit. CSVT in children is often multifactorial in etiology such as infection, dehydration, prothrombotic conditions, cerebrovascular injury, as well as acute and chronic medical conditions such as anemia, congenital heart disease, nephrotic syndrome, systemic lupus erythematosus, and malignancy. Case: A previously healthy 17-year-old girl visited for sudden hemiplegia of right extremities and left-sided headache one day ago. Initial magnetic resonance imaging (MRI) showed edematous change with multifocal hemorrhage involving left parietal lobe. Mannitol was started to reduce intracerebral pressure. She had two times of generalized tonic seizures 9 days later and unremitting hemiplegia. Follow-up MRI with angio/venogram revealed the increased swelling and extent of previous lesion and filling defects within superior sagittal sinus and left transverse sinus, which was consistent with venous infarction and CSVT. She was given medication of low-molecular-weight heparin (enoxaparin, 1 mg/kg bid), and her neurologic deficit was significantly improved. Comprehensive examinations for the causes and risk factors of CSVT were performed, and none of the etiologies was discovered. After the medication of subcutaneous heparin during 3 months, warfarin has been maintained monitoring of prothrombin time INR until now. The last MRI showed the decreased extent of the venous infarction. Conclusion: Spontaneous attack of CSVT is very few in healthy children with none of risk factors. When children have sudden focal neurologic deficit such as hemiplegia, we should consider the neuroimaging with detailed angio/venography.