Black‐bone silky fowl (Gallus gallus domesticus Brisson), medicinal food homology, utilizes to enhance human immunity. However, it remains unclear whether Black‐bone silky fowl melanin (BSFM), one of its bioactive components, could affect immune function. The purpose of this study is to examine the immunoregulatory effect and the underlying mechanism of BSFM in the cyclophosphamide‐induced immunosuppressive mice model. The findings revealed that BSFM could significantly increase white blood cells (WBC) in peripheral blood; upregulate the expression of IL‐4, TNF‐α, and M‐CSF in the plasma; and reduce tissue damage. Mechanistically, proteomics has revealed that BSFM therapy substantially affected the quantity of 29 proteins (Mtatp6, Cst3, Pglyrp1, Igkc, and other targets), which mostly participate in the phosphatidylcholine catabolic process, positive regulation of type IIa hypersensitivity, lipid catabolic process, and neutrophil chemotaxis. Metabolomics indicated that BSFM reduced the levels of Octanoylglucuronide, Gly‐Gly, and N‐alpha‐acetyl‐ornithine and modulated arginine biosynthesis. Furthermore, BSFM treatment modified the composition of gut microbiota and increased the relative abundance of Prevotella, S24‐7, Olsenella, Lactococcus, hgcl‐clade, Parasutterella, and Acetobacter. A significant correlation modified the composition of gut microbiota among inflammation‐associated parameters, gut microbiota, and various metabolites (DMs) through Pearson correlation analysis. These findings suggest that BSFM holds promise in enhancing the human immune system and may serve as a complementary therapy in conventional chemotherapy.