We examined the effect of spinal cord-derived neural stem/progenitor cells (NSPCs) after delayed transplantation into the injured adult rat spinal cord with or without earlier transplantation of bone marrow-derived mesenchymal stromal cells (BMSCs). Either BMSCs or culture medium were transplanted immediately after clip compression injury (27 g force), and then, 9 days after injury, NSPCs or culture medium were transplanted. Cell survival and differentiation, functional recovery, retrograde axonal tracing, and immunoelectron microscopy were assessed. A significant improvement in functional recovery based on three different measures was seen only in the group receiving NSPCs without BMSCs, and the improved recovery was evident within 1 week of transplantation. In this group, NSPCs differentiated mainly into oligodendrocytes and astrocytes, there was ensheathing of axons at the injury site by transplanted NSPCs, an increase in host oligodendrocytes, and a trend toward an increase in retrogradely labeled supraspinal nuclei. Transplantation of the BMSC scaffold resulted in a trend toward improved survival of the NSPCs, but there was no increase in function. Thus, transplantation of adult rat NSPCs produced significant early functional improvement after spinal cord injury, suggesting an early neuroprotective action associated with oligodendrocyte survival and axonal ensheathment by transplanted NSPCs.