Primary gliosarcoma (GS) in the spinal cord is extremely rare. To our knowledge, there are only two cases reported in the literature. The clinical feature, treatment, and prognosis for this rare entity have been uncertain. In this paper, we present a unique case of histopathologically proven primary intramedullary spinal GS without intracranial involvement. A 46-year-old male presented with a 3-month history of progressively worsening numbness and weakness of his left leg and gait instability. Spinal magnetic resonance imaging revealed an intramedullary lesion at the level T4-7 with irregularly heterogeneous enhancement. Intracranial or other bodies' lesions were absent. The patient underwent a T4-7 laminectomy and subtotal tumor removal was achieved. Histopathological findings confirmed a GS. Postoperatively, the patient received adjuvant radiotherapy combined with concurrent and adjuvant chemotherapy with Temozolomide. However, he had tumor recurrence 5 months after surgery and experienced a progression of paraplegia with rapid enlargement of residual tumor. The patient died of severe pneumonia and respiratory failure 6 months after diagnosis. The clinical features and treatment outcome of this rare entity are discussed along with a review of the relevant literature. Primary GS should be considered in the differential diagnosis of spinal cord tumors. Multidisciplinary treatment including surgical resection and adjuvant radiochemotherapy should be performed as standard protocol due to highly malignant nature, although overall prognosis of this tumor is poor.