Data regarding vitamin D in multiple sclerosis (MS) in Asia are limited. We investigated whether Japanese MS patients show decreased serum 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH)2D], and vitamin D-binding protein (DBP) during winter. Mean serum 25(OH)D and 1,25(OH)2D levels were significantly lower in MS patients than in controls. There were no significant differences in serum 25(OH)D, 1,25(OH)2D, and DBP levels between patients or between controls from northern Japan (Hokkaido) and southern Japan (Kyushu). Serum vitamin D levels were low in Japanese MS patients but did not differ in patients from northern and southern Japan.