The efficacy and safety of growth promoters as immunopotentiators in chickens have been extensively evaluated under laboratory conditions. In this study, 210 (day old chicks) chicks were allotted into seven groups. Group 1 served as a control, group 2 and 3 were fed Reomin. Group 4 and 5 were supplemented with Gibberellic acid, a plant hormone with androgenic features, through drinking water (single and double doses). Group 6 and 7 were fed Digestamin supplemented to basal diet at recommended single and double doses. All chicks were vaccinated against H5N1twice at three weeks interval. Blood samples as well as tissue specimens were collected for assessment of T-Lymphocyte Proliferation Assay (LPA), differential leucocyte count, serum total protein and albumin and interleukin-2 (IL-2) production. Furthermore, wattle dermal reaction was conducted. The Gibberellic acid treated groups showed highest lymphocytic count and IL-2 production. Meanwhile chickens treated with probiotics showed highest values of LPA, total serum proteins and globulin as well as wattle dermal thickness. These results indicated that the evaluated growth promoters are safe and efficacious for enhancing immune response against H5N1antigen.