AbstractGenistein (GEN) is mainly extracted from soy plants and has potential functions as an antioxidant and in promoting immune function and growth. This study evaluated the effects of feeding breeders and their offspring dietary GEN on the immune function and growth performance of broiler chicks. Breeders were assigned to a control diet or GEN diet (control diet +400 mg/kg GEN), and their offspring were fed a control diet or GEN diet (control diet +40 mg/kg GEN). GEN treatment increased the body weight gain, tibial length, tibial width and slaughter performance of broilers and decreased the feed conversion ratio. The treatment also affected skeletal muscle myosin assembly and growth and increased growth hormone levels and IGF-I and IGFBP1 expression. Following GEN treatment, antigen processing and presentation, macrophage activation, B lymphocyte, NK cell and helper T cell proliferation, and CD4+ T lymphocyte differentiation all increased significantly. Increases were also observed in IgM and IgG concentrations, antibody titers, and antioxidant capacity. In addition, GEN treatment activated the Toll-like receptor signaling pathway and MAPK cascade signaling pathway. In summary, dietary GEN supplementation for breeders and their offspring can improve the growth performance and immune function of broiler chicks.