Arachnoid cyst (AC) is a neurological complication of autosomal dominant polycystic kidney disease (ADPKD). Although an AC can increase the risk of a subdural hematoma, the clinical presentation of bleeding into an AC associated with ADPKD is not well known. We herein report the case of a 59-year-old woman in whom the initiation of hemodialysis for renal failure led to AC bleeding. A change of anticoagulant from heparin to nafamostat mesilate allowed dialysis to continue without rebleeding. These findings suggest that hemodialysis in patients with an AC associated with ADPKD may increase the risk of bleeding. Nafamostat mesilate may be useful in such cases.