Mulberry branch flavonoids(MBFs) have garnered significant attention as natural feed additives and antioxidants; however, their antioxidant properties in meat post-slaughter and their influence on muscle-related metabolic processes remain largely unexplored. Herein, we evaluated the effects of MBFs on the antioxidant capacity and metabolic processes of muscle in yellow broilers. The results demonstrated that MBFs enhanced the activity of antioxidant enzymes in muscle tissue. Specifically,real-time quantitative PCR(RT-PCR) analysis revealed that MBFs increased the expression of antioxidant enzyme genes in a dose-dependent manner, activating the Nrf2 signaling pathway, and upregulating the expression of the Nrf2 gene and its downstream targets at doses up to 3,000 mg/kg. Furthermore, the results of widely targeted metabolomics indicated that the dietary supplementation of MBFs changed the amino acid profile of muscle, increasing the levels of amino acids and small peptides that contribute to antioxidant properties, while also reducing the content of oxidized lipids, carnitine(C5:1), and partially lysophosphatidylcholine(LPC). Notably, at doses up to 3,000 mg/kg, the levels of five signature bile acids increased in correlation with the added dose. KEGG analysis indicated that the differential metabolites were predominantly enriched in the metabolism of xenobiotics by cytochrome P450, suggesting that the function of MBFs may be associated with the expression of P450 enzymes. In summary, this study demonstrates that MBFs are effective and safe natural antioxidants that can mitigate oxidative damage associated with intensive livestock and poultry farming.~1