Superior sagittal sinus thrombosis (SSST) is associated with a variety of hypercoaguable states. Although coagulation disturbances are reported in hyperthyroidism, a direct link between hyperthyroidism and cerebral venous thrombosis is not established. We report a 39-year-old man who developed increased intracranial pressure, seizures, and rapid atrial fibrillation. Neuroimaging showed SSST, and laboratory studies were consistent with hyperthyroidism. No other causes of a hypercoaguable state were identified. Prompt treatment of his hyperthyroidism led to recanalization of the superior sagittal sinus and a full neurological recovery. Given the known effects of hyperthyroidism on factor VIII activity, we hypothesize that hyperthyroidism is an independent risk factor for SSST. A high index of suspicion for SSST is warranted in patients with hyperthyroidism and neurological symptoms. Furthermore, thyroid dysfunction should be excluded in patients with unexplained SSST