The senior dog population (ages 7+) is increasing worldwide because of a larger interest in the health of companion dogs. In this study, we aimed to develop dog foods via fermentation to address the nutritional needs of senior dogs. The dog food ingredients were fermented with candidates of starter culture and then the fermentation efficiency was compared using pH and ammonia nitrogen for selection of optimum strains. The fermentation was carried out with a moisture content of 60% and starter culture of 1.0×107 cfu/g at 3 7℃ for 24 h. And there were manufactured pre- and post-senior dog foods (treatments) including fermented rice, fermented pinto bean, and fermented soybean meal and it compared with non-fermented dog foods (controls) on fermentation characteristics, in vitro dry matter and crude protein digestibility, and palatability. As results of this study, fermentation efficiency was higher when rice or wheat was inoculated with Lactobacillus brevis (ΔpH; -2.74 ~ -2.94) and meat and bone meal with Lactobacillus reuteri (ΔNH3-N conc.; 4.29 g/L). The ammonia nitrogen level, total volatile fatty acid content, in vitro dry matter and crude protein digestibility of L. brevis-fermented dog food were significantly greater than those of non-fermented dog food (p<0.05). Further, in case of palatability tests, fermented foods tended to have higher palatability compared to non-fermented foods, and no negative effect was observed in fermented foods. These results suggest that fermented food is suitable for senior dogs and could help to maintain adult dog health.