We present a rare case of cerebral venous sinus thrombosis associated with long-term and high-dose use of sildenafil. A 29-year-old man was referred to our neuroophthalmology clinic for bilateral visual deterioration and severe headache. He had stage 2 papilledema and other clinical and neurological examinations were normal. He had used the drug for nearly 2 years, two to three times a day. All laboratory parameters including blood count cell, coagulation panels, and genetic tests including methylene-tetrahydrofolate reductase and factor V Leiden mutation were unremarkable. The brain magnetic resonance imaging result confirmed transverse cerebral venous sinus thrombosis (CVST). The opening pressure of cerebrospinal fluid (CSF) was 43 cm H2O with normal biochemistry and no cells. Clinicians must be aware of the possibility of CVST when the patient uses sildenafil.