Rosai-Dorfman disease is a rare, non-neoplastic lymphoproliferative disorder that is characterized by its specific histological features. However, it is uncommon for it to involve the thoracic spinal cord as a site of extranodal disease. A 36 year-old man developed progressive paraparesis 2 weeks prior to admission. On an MRI study, the spinal cord was compressed at the T4 and T5 levels posteriorly by an epidural mass. A decompressive laminectomy and removal of the mass were performed and Rosai-Dorfman disease was confirmed histologically. After the operation, additional high-dose radiotherapy was performed. The motor weakness and hypesthesia in the lower extremities resolved completely and there was no evidence of recurrence at the final follow-up examination.