Delayed transplantation of neural stem/progenitor cells (NS/PCs) into the injured spinal cord can promote functional recovery in adult rats and monkeys. To enhance the functional recovery after NS/PC transplantation, we focused on galectin‐1, a carbohydrate‐binding protein with pleiotropic roles in cell growth, differentiation, apoptosis, and neurite outgrowth. Here, to determine the combined therapeutic effect of NS/PC transplantation and galectin‐1 on spinal cord injury (SCI), human NS/PCs were transfected by lentivirus with galectin‐1 and green fluorescent protein (GFP), (Gal‐NS/PCs) or GFP alone (GFP‐NS/PCs), expanded in vitro, and then transplanted into the spinal cord of adult common marmosets, 9 days after contusive cervical SCI. The animals' motor function was evaluated by their spontaneous motor activity, bar grip power, and performance on a treadmill test. Histological analyses revealed that the grafted human NS/PCs survived and differentiated into neurons, astrocytes, and oligodendrocytes. There were significant differences in the myelinated area, corticospinal fibers, and serotonergic fibers among the Gal‐NS/PC, GFP‐NS/PC, vehicle‐control, and sham‐operated groups. The Gal‐NS/PC‐grafted animals showed a better performance on all the behavioral tests compared with the other groups. These findings suggest that Gal‐NS/PCs have better therapeutic potential than NS/PCs for SCI in nonhuman primates and that human Gal‐NS/PC transplantation might be a feasible treatment for human SCI. © 2010 Wiley‐Liss, Inc.