Spinal cord injury (SCI) significantly impacts patients’ health and quality of life. Current medical, surgical, and rehabilitative treatments often fall short in addressing long-term complications, particularly in cases of complete paralysis. The transplantation of autologous bone marrow-derived mononuclear cells (BM-MNCs) has emerged as a promising approach for SCI treatment, offering key advantages such as minimal immune rejection, fewer side effects, and notable improvements in motor and sensory functions. Unlike other therapies, this method does not require laboratory cell culture, simplifying its application. In this chapter, we describe the step-by-step procedure for isolating autologous BM-MNCs from patients and transplanting them into the spinal canal to treat SCI. Our aim is to provide readers with a clear understanding of this innovative process and a comprehensive overview of its clinical application in SCI treatment.