This experiment was carried out on three hundred white Arbor Acres day-old chicks to study the effect of different stocking densities on bird performance as well as on their immune response against Newcastle disease (ND) and injected sheep red blood corpuscles (SRBCs). At the age of 4th week the chicks were classified into three main groups, group A (10 bird /m2, group B (15 bird/ m2) and group C (20 bird/ m2). All the three groups were vaccinated against ND and injected with SRBCs (at 4th week of age), the average body weight, feed conversion and antibodies titers were estimated for all groups. The results revealed that body weight, feed conversion and estimated titers were significantly affected with higher stocking densities resulting in a significant reduction in body weight and immune response of groups B & C in comparable to those of group A.