Protein C exerts anticoagulatory effects by inactivating factor V and VII and stimulating fibrinolysis. Hereditary protein C-deficient individuals have an increased risk of venous thrombosis and thromboembolism at young age. To our knowledge, the deep cerebral venous thrombosis associated with protein C deficiency has not been reported in Korea. A 34-year-old man was admitted to our hospital because of sudden onset of headache with nausea, vomiting and ocular pain. He had suffered from recurrent deep vein thrombosis of the right lower extremity for one year. Brain MRI showed thrombosis of the straight and confluent sinuses and venous infarction of the right thalamus. The result of cerebral angiography corresponded to MRI findings. Protein C antigen concentration was decreased to 65% and its functional activity was 37%. Other coagulation test and routine blood examination was normal. The protein C level of his mother was low in both antigen and activity, but protein C levels of three siblings were normal in functional activity. We speculate that the etiology of the deep cerebral venous thrombosis in this patient is associated with protein C deficiency and suggest it is valuable to measure protein C level in patients with cerebral venous thrombosis.