We report a case of cerebral venous thrombosis related to the ingestion of tadalafil. A 45-year-old man presented with posterior headache and was diagnosed with tension headache. Five days later, he was transported to our hospital via ambulance due to a tonic-clonic seizure. Head MRI showed cerebral venous thrombosis (CVT). He confessed to having recently taken a large doses of tadalafil. His anti-cardiolipin antibody and anti-caldiolipin-β2-glycoprotein-I complex antibody levels were elevated. Our case suggests the possibility that tadalafil is related to both cardiovascular complications and CVT in patients with hypercoagulability. Patients with conditions associated with hypercoagulability, including antiphospholipid syndrome may be better advised to avoid the use of tadalafil.