Chronic subdural hematoma (CSH) in the posterior fossa is extremely rare. The surgical strategy is still controversial. We report a case of bilateral CSH in the posterior fossa successfully treated with a single-burr hole surgery. A 74-year-old man under anticoagulation and antiplatelet therapy developed headache and nausea during observation for an asymptomatic supratentorial CSH. Radiological examinations revealed appearance of bilateral CSH in the posterior fossa associated with hydrocephalus. Upon rapid deterioration of the patient's consciousness, an urgent treatment was required. A burr hole was made near the transverse-sigmoid junction on the left side to access the hematoma. No ventricular drainage was placed as his consciousness improved during the decompression of the hematoma. Postoperative computed tomography showed that bilateral CSH and hydrocephalus had been successfully treated. In bilateral CSH in the posterior fossa, there may be a connection between each side. CSH in the posterior fossa, when urgent, can be treated under local anesthesia with a unilateral burr hole irrigation.