To investigate the immunomodulatory effects of the combination of a probiotic complex and oligofructose on mice, an immunocompromised mouse model was successfully established by injecting cyclophosphamide according to the Methods for Testing and Evaluating the Functions of Health Foods (2023 Edition), thereby reducing the immune function of mice. The effects of low, medium, and high (6×106, 6×107, and 6×108 CFU each) doses of combined probiotic complex and oligofructose (1.5 mg/pc) on body weights, immune organ indices, and cellular, humoral, and nonspecific in immunocompromised mice were determined. The experimental results showed that the co-infusion of probiotic complex and oligofructose resulted in a significant increase in the body weight, thymic index, and splenic index of immunocompromised mice, with the latter two in the high-dose group increasing by 104.15% and 46.12%, respectively, suggesting an improvement in the pathological characteristics of the thymus and spleen. Moreover, in the high-dose group, the optical density difference value, foot plantar thickness, hemolytic empty spot number, half hemolytic value, phagocytic index α, phagocytic index, and NK cell activity increased by 83.87%, 94.12%, 51.49%, 31.83%, 46.53%, 54.29%, and 86.92%, respectively, compared with values in the model group, indicating significantly improved cellular, humoral, and non-specific immunity in immunocompromised mice. Levels of the serum cytokines IL-2, IL-6, and TNF-α also increased in a dose-dependent manner. These findings indicate that the administration of a probiotic complex and oligofructose to mice can enhance their immune function.