Abstract: This study aimed to investigate the immunoenhancing effects of sturgeon caviar on cyclophosphamide (CTX)-induced immunosuppressed mice. ICR (Institute of Cancer Research, ICR) mice were intraperitoneally injected with CTX to establish an immunocompromised model. The immunocompromised mice were then fed diets supplemented with low (4.2 g/kg), medium (8.4 g/kg), and high (16.8 g/kg) doses of hybrid sturgeon caviar, and the control group was fed diets without caviar for 30 days. Hematoxylin-eosin staining was used to examine the spleen tissue morphology of mice, and the immune organ indexes, immune cell capabilities, immune enzyme activities and immune-related cytokine levels in each group were analyzed. The results showed that compared with the model group, the high-dose caviar group significantly increased the daily feed intake and body weight of mice and alleviated intestinal villus damage. The high-dose caviar significantly increased the spleen and thymus organ indices, as well as the phagocytic capacity and proliferative activity of macrophages in mice by 31.1%, 40.1%, 25.2%, and 48.5% (P<0.05). The high-dose caviar extremely significantly increased the proliferation activity of T and B lymphocytes by 32.9% and 50.9%, respectively (P<0.01). The medium-dose caviar significantly increased the activity of lactate dehydrogenase and acid phosphatase by 33% and 13.4%, respectively (P<0.05), and the high-dose caviar extremely significantly increased the lysozyme activity by 53.4% (P<0.01). The high-dose caviar significantly enhanced the mRNA expression levels of interleukin-2 (IL-2), interleukin-12 (IL-12), and tumor necrosis factor-α (TNF-α) in spleen immune cells, with increases of 86.9%, 86.1%, and 91.5%, respectively (P<0.05). The low-dose caviar significantly increased the mRNA expression level of interleukin-6 (IL-6) by 64.5% (P<0.05). Additionally, the high-dose caviar significantly promoted the secretion of IL-2, IL-12, and TNF-α in serum (P<0.05), with increases of 52.1%, 30.6%, and 5%, respectively. The medium-dose caviar extremely significantly increased the secretion of IL-6 by 57.8% (P<0.01). In conclusion, caviar can alleviate CTX-induced intestinal damage in mice, facilitate the recovery of intestinal villi, and enhance the cellular immunity, humoral immunity, and non-specific immunity suppressed by CTX, thereby enhancing the body's immune regulatory capacity.