Immunomodulators are substances that able to regulate or modulate immune responses. In order to investigate the lactoferrin effect on the immune system of broiler chickens,one hundred twenty (1-day-old) chicks of both sexes were randomly allocated into 2 dietary groups (60 chicks/group), group1 (G1): chicks were offered basal diets and kept as control group, group2 (G2): Chicks were offered basal diets supplemented with lactoferrin (250mg/kg diet for 6 weeks). Evaluating the effects of dietary supplementation with lactoferrin on growth performance of broiler chicks, humeral immunity by measuring antibody titer against Newcastle (ND) and Avian influenza (AIV)vaccine, and on innate immunity by measuring some functions of peripheral blood monocytes (PBM) as phagocytic activity, fungicidal activity, nitric oxide (NO) production and reactive oxygen species (ROS) production by tetrazolium reduction test. To study antibacterial effect of lactoferrin, challenge test was carried out using virulent E. coli strain .The results revealed that, lactoferrin improve growth performance and could stimulate the humeral immunity by increasing the antibody titer aginst ND and AIV vaccine .Also lactoferrin could enhance the innate immunity by significant increasing of phagocytic and Fungicidal activities of PBM and its production of ROS and NO. Lactoferrin have the ability to protect broiler chickens from virulent agents as E. coli. Therefore, lactoferrin may be used as immunostimulant, growth promoters and antibacterial agent in broiler chickens.