This double-blind randomized study evaluated the therapeutic effect of low-power laser irradiation (LPLI) on peripheral nerve regeneration, after complete transection and direct anastomosis of the rat sciatic nerve. After this procedure, 13 of 24 rats received postoperative LPLI, with a wavelength of 780 nm laser, applied transcutaneously, 30 min daily for 21 consecutive days, to corresponding segments of the spinal cord and to the injured sciatic nerve. Positive somatosensory evoked responses were found in 69.2 percent of the irradiated rats (p = 0.019), compared to 18.2 percent of the non-irradiated rats. Immunohistochemical staining in the laser-treated group showed an increased total number of axons (p = 0.026), and better quality of the regeneration process, due to an increased number of large-diameter axons (p = 0.021), compared to the non-irradiated control group. The study suggests that postoperative LPLI enhances the regenerative processes of peripheral nerves after complete transection and anastomosis.