This case report describes a 66-year-old male who presented with progressive paraparesis after falling down. Magnetic resonance (MR) imaging showed an acute spinal hematoma at the T11-T12 level with spinal cord compression. The patient underwent an emergency left T11-T12 hemilaminectomy. The location of hematoma was subarachnoidal and the source of bleeding was the injured radicular vein. To the best of our knowledge, this is the first case of traumatic spinal subarachnoid hematoma. We discuss the possible mechanism and our case illustrates an injured radicular vein can be a source of traumatic spinal subarachnoid hematoma.