Transcranial direct current stimulation (tDCS) of the primary motor cortex of the lower limb has been exploited in the treatment of patients with stroke and spastic lower limb paresis. We examined this stimulation efficacy in the treatment of multiple sclerosis (MS)-related walking disability. In a single-center randomized double-blind clinical trial study, 13 patients with MS and walking disability and Expanded Disability Status Scale (EDSS) score of 3 to 6 were randomized to the real and sham stimulation groups. In the real tDCS stimulation, 7 patients received anodal 2.5 mA stimulation at 1 cm anterior to the C point for 30-minute daily sessions in 7 consecutive days. The other group received sham stimulation with the same protocol. The primary outcome of the trial was change in the Timed 25-Foot Walk (T25-FW) from before to after the stimulation. We also assessed the Multiple Sclerosis Walking Scale-12 (MSWS-12). We employed linear mixed effects model to examine the efficacy of tDCS stimulation on changing the outcomes. On average, patients who received real tDCS stimulation walked faster after 7 sessions of stimulation [Estimate = -2.7, standard error (SE) = 1.3, P = 0.049], while walking speed of sham stimulation recipients did not change. For every session of stimulation, recipients of real tDCS stimulation spent 2.7 seconds less for walking the 25 feet. Real tDCS stimulation was not effective in improving MSWS-12 scores. tDCS stimulation of the lower limb motor cortex speeded up patients with MS in walking, but without improvement in patients' mobility in daily activities.