Oral and esophageal candidiasis sometimes leads to mucosal hyperplasia, and progresses to carcinoma. We have produced an animal model for hyperplastic mucosal candidiasis in the forestomach that has a proliferative lesion of the squamous epithelium with chronic inflammation and C. albicans infection, some of which advanced to squamous cell carcinoma. There are many reports of the antibacterial effects of probiotics, but consensus about their antifungal effect has not been reached. In the present study, we investigate whether probiotic (yogurt) containing Lactobacillus gasseri OLL2716 (LG21 yogurt) can prevent proliferative and inflammatory changes caused by C. albicans in this mucosal candidiasis animal model. Diabetes was induced in 8-week-old WBN/Kob rats by intravenous administration of alloxan. One group of diabetic rats received a saline containing C. albicans and LG21 yogurt orally (DC+LG21 group) for 30 weeks, and another group received only C. albicans (DC group) for 30 weeks. They were sacrificed at 40 weeks of age, and analyzed histopathologically. In the DC+LG21 group, squamous hyperplasia at the greater curvature was significantly milder, and the Ki-67 positive index was significantly lower compared with the DC group. Suppurative inflammation with C. albicans also tended to be suppressed at the greater curvature. These findings suggest that probiotic (yogurt) containing Lactobacillus gasseri OLL2716 can suppress squamous hyperplastic change and inflammation associated with C. albicans infection in the forestomach.