Study design: The use of stem cells for functional recovery after spinal cord injury. Objective: The aim of this study was to evaluate the effects of a combination of autologous undifferentiated and neural-induced bone marrow mesenchymal stem cells (MSCs) on behavioral improvement in rats after inducing spinal cord injury and comparing with transplantation of undifferentiated and neural-induced MSCs alone. Setting: The study was conducted at the department of Clinical Sciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran. Methods: The spinal cord was injured by contusion using a Fogarty embolectomy catheter at the T8–T9 level of the spinal cord, and autologous MSCs were transplanted into the center of the developing lesion cavity, 3 mm cranial and 3 mm caudal to the cavity, at 7 days after induction of spinal cord compression injury. Results: At 5 weeks after transplantation, the presence of transplanted cells was detected in the spinal cord parenchyma using immunohistochemistry analysis. In all treatment groups (differentiated, undifferentiated and mix), there was less cavitation than lesion sites in the control group. The Basso–Beattie–Bresnahan (BBB) score was significantly higher in rats transplanted with a combination of cells and in rats transplanted with neural-induced MSCs alone than in undifferentiated and control rats. Conclusion: Pre-differentiation of MSCs to neuron-like cells has a very important role in achieving the best results for functional improvement.