We herein describe a case of acute spinal subdural hematoma (SSDH) during the administration of high-dose corticosteroids and intravenous heparin for the treatment of active lupus nephritis. After SSDH was promptly diagnosed using magnetic resonance imaging (MRI), the patient recovered well with conservative treatment involving the discontinuation of heparin sodium. Although SSDH is a rare complication, it should be considered as a cause of neurological manifestations in patients with active systemic lupus erythematosus.