Interruption of spinal cord continuity remains an incurable condition that leads to functional loss below the lesion level. Effective treatment to enable spinal cord regeneration is lacking, although cell therapy is an evolving opportunity. Therefore, the purpose of this study was to evaluate the safety and potential efficacy of multiple Wharton jelly mesenchymal stem cell transplants in a patient with a spinal cord injury. A patient with incomplete spinal cord interruption at the T11 to T12 vertebrae was enrolled in experimental therapy. The patient scored A/B on the ASIA scale (developed by the American Spinal Injury Association) with deep paraparesis and sphincter palsy. However, full ability to fix the patient's trunk upon admission was confirmed. Bilateral axonal damage of motor and sensory neural fibers of lower extremities was confirmed with electromyography and electroneurography. One year of standard therapy did not bring any positive results. The patient underwent 5 rounds of Wharton jelly mesenchymal stem cell transplants every 3 months (total treatment time of 18 months). There were no complications connected with therapy during the 18- month follow-up. Continuous neurological and quality of life improvements were seen after every transplant. The patient's ASIA score changed from A/B to C/D and from 112 to 231 points. The sensation level decreased from the T12 to L3 to L4 level. The patient regained bladder control and anal sensation. Muscle strength at the left lower extremity improved. The patient gained the ability to stand in a standing frame and walk with an orthosis. Neurophysiological examinations objectively confirmed the improvement. Magnetic resonance imaging demonstrated no changes in the spinal cord signal. The treatment demonstrated an objective improvement that could be used for patients with chronic thoracic incomplete spinal cord injury.