A 36-year-old female was admitted with leptomeningeal melanoma associated with straight sinus thrombosis manifesting as headache and vomiting. Computed tomography and magnetic resonance imaging showed the subarachnoid space was diffusely enhanced. Her consciousness rapidly deteriorated to a coma. Angiography demonstrated straight sinus thrombosis. Thrombolysis by superselective catheterization and infusion of urokinase was successfully performed. She recovered consciousness, but developed paraparesis 2 weeks later. Malignant melanoma with meningeal dissemination was diagnosed by an open biopsy of the lumbar lesion. Angiitis induced by the infiltration of tumor cells and activation of the blood coagulation cascade was probably the causative mechanism of the sinus thrombosis.