Intracranial subdural haematoma has been reported to be an exceptionally rare complication of accidental dural puncture. An accidental lumbar dural puncture occurred in a 36-yr-old male undergoing orthopedic knee surgery. On the morning after the operation, the patient complained of severe occipital headache, although this was relieved with loxoprofen and rest. This was assumed to be a postdural puncture headache (PDPH) because it had a postural component (it was worse on sitting up). On the third day after the operation, the patient developed a severe diffuse headache together with nausea, which did not subside with analgesia and bed rest. Magnetic resonance imaging of the head showed a small acute subdural hematoma in the bilateral temporooccipital region with no mass effect. The patient was conscious and oriented. There was no focal neurological deficit. The patient was managed conservatively with bed rest and intravenous fluids. His condition improved without surgical decompression and was discharged on the 40 th day after the operation. Severe and prolonged PDPH shoud be considered as a warning sign of an intracranial complication.