Abstract: The influence of delayed feeding on the performance, development and response of immune system to Newcastle disease vaccination were investigated. 72 day old cockerel chicks purchased from a local hatchery were used. These were at the onset divided into two groups A and B of equal numbers (n = 36) and housed separately. Group A was provided with a diet containing 25% crude protein and 2800Kcal of metabolizable energy from the day of hatch while group B was deprived of feed for the first 72 h post hatch (ph) after which they were introduced to feed and thereafter maintained on same diet as group A. Once feeding is commenced in each of the groups, same regimen was maintained till the end of the study. Other brooding arrangements were common to the groups. 21 days ph 12 chicks were randomly selected per group, weighed, sacrificed after which two blood samples were collected for general haematology and serum biochemistry respectively. They were then necropsied and lymphoid organs as bursa of fabricius, spleen and caecal tonsil as well as liver harvested weighed and their relative weights calculated. The remaining 24 chicks per group were then vaccinated with Newcastle Disease (ND) vaccine lasotaR. Five days later, 12 chicks were again randomly elected per group and same operations as on day 21 carried out on the chicks. On day 42 ph, all the remaining chicks in each of the groups were vaccinated against ND using ND vaccine komarovR and 5 days later, they were sacrificed and again all the activities of day 21 repeated. Our results showed that delaying feeding for up to 72 h ph does not significantly affect the growth, development and function of some organs of the immune system. Moreover, it also produced no effect on Packed Cell Volume early in life as significant variation between the two groups (p<0.05) was only observed on day 47 ph. However, our finding showed that early feeding significantly improved early response to vaccinations (p<0.05) shown by higher geometric mean antibody titre. There were no differences in organ morphology and histopathology between the two groups. The study demonstrated that early feeding could be beneficial in the response of chicks to early vaccinations but does not confer other productive advantage.