This study aimed to assess the effect of ascorbic acid supplementation on fecal immunoglobulin A (IgA) in calves. A total of 30 Japanese Black calves were assigned to the supplementation and control groups. The supplementation group received 1,000 mg/day of ascorbic acid orally from 2 to 4 weeks of age (n = 15), whereas the control group did not (n = 15). Blood and fecal samples were collected at 2 and 4 weeks of age. There is no significant difference in the values of hematological and biochemical parameters between the two groups. The fecal IgA concentration in the control group decreased from 2 to 4 weeks of age, whereas it increased in the supplementation group from 2 to 4 weeks of age. The difference between the groups was statistically significant at 4 weeks of age (P < 0.05). These results suggested that ascorbic acid supplementation to calves may increase IgA production in the intestinal tract.