Aims: To investigate the influence of heat-killed Lactobacillus gasseri TMC0356 on changes in respiratory immune function and intestinal microbiota in a diet-induced obese mouse model. Methods and Results: Male C57BL/6J mice were fed a high-fat diet for 16 weeks. After 8 weeks, the high-fat-diet-induced obese mice (DIO mice) were randomly divided into two 0067roups, the DIO and DIO0356 groups. DIO0356 group mice were orally fed with heat-killed TMC0356 every day for 8 weeks, while DIO group mice were exposed to 0.85% NaCl over the same time period as controls. After intervention, the pulmonary mRNA expression of cytokines and other immune molecules in DIO0356 mice compared to those in DIO group mice was significantly increased (P < 0.05, P < 0.01). In faecal bacterial profiles, analysed using the terminal restriction fragment length polymorphism (T-RFLP) method, T-RFLP patterns in 75% of the DIO0356 group mice were apparently changed compared with those in control group mice. Conclusion: These results suggest that inactive lactobacilli may stimulate the respiratory immune responses of obese host animals to enhance their natural defences against respiratory infection, partially associating with their potent impact on intestinal microbiota. Significance and Impact of the Study: We have demonstrated that oral administration of inactive lactobacilli may protect host animals from the lung immune dysfunction caused by obesity.