In athletes, repeated intensive exercise is considered to depress the immune system. The purpose of this study was to investigate the effects of yogurt fermented with Lactococcus lactis subsp. cremoris FC (L. cremoris FC) on salivary secretory immunoglobulin A (SIgA) in long-distance runners (high school students) during a 5 day intensive training program. Fourteen subjects were divided into 2 groups: a yogurt fermented with L. cremoris FC intake group and a milk intake group (control group). Each subject consumed yogurt or milk for 5 days during the intensive training. Salivary samples were obtained on days 1 and 5, and SIgA secretion and cortisol levels were measured. In addition, the mood of each subject was evaluated using the Profile of Mood States (POMS) questionnaire. Our study suggested that L. cremoris FC intake increases SIgA secretion. In addition, there might be a significant suppression in the increase of salivary cortisol levels caused by exercise mainly, but there was no effect on mood. These results suggest that L. cremoris FC intake may have health benefits by enhancing oral immune function mediated by SIgA.