The homeostatic systems, such as the nervous and immune systems, show deterioration in aging as a consequence of the age-related oxidative-inflammatory stress establishment. The supplementation with fermented milk containing probiotic bacteria could be a good nutritional strategy to improve homeostatic system functions in aged individuals through the modulation of their redox state. The aim of the present study was to evaluate the effect of 2-week supplementation with a commercial fermented milk containing yogurt species (Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus), and the probiotic Lactobacillus casei DN-114001 on behavior, redox state, and immune cell functions of aged mice as well as on their life span. Aged female ICR-CD1 mice were supplemented with fermented milk containing these probiotics for 2 weeks. After this period, a variety of behavioral tests were performed and several parameters of redox state and function of peritoneal leukocytes were analyzed. The results showed that the 2-week supplementation of fermented milk containing probiotics improved behavior (such as muscular vigor, exploratory activity, and anxiety-like behavior) as well as the redox state and functions of peritoneal immune cells in aged mice. In conclusion, the present study shows that the supplementation with fermented milk containing probiotics for a short period of time could be a good nutritional strategy to promote healthy aging.