Arachnoid cyst (AC) is usually asymptomatic, incidentally-found, and a well-known risk factor of developing chronic subdural hematoma (CSDH) after minor head injury in young patients. Spontaneous remission or rupture of arachnoid cyst is very rare. When chronic subdural hematoma occurs, burr hole drainage is indicated if mass effect presenting. Only the hematoma is drained, where the cyst is left untouched. Although the chance of an arachnoid cyst to disappear is low, here we presents a case where the AC disappears after burr hole operation. We subsequently discuss the possible pathophysiological mechanisms and the relevant literatures.