Sixty chickens were randomly divided into two groups (30 chickens in each group) to determine the effect of oral administration of chicken intestinal antimicrobial peptides (CIAMP) on the humoral immune response. Chickens of both groups were fed the same diet. In the treatment group chickens received drinking water supplemented with CIAMP (1 microg/ml) right after hatching. Samples of blood, bursa of Fabricus, spleen and intestine were taken at day 1, 4, 7, 10 and 17 of experiment. CIAMP supplementation enhanced the content of IgG and IgM in serum from day 4-10 and day 10-17, respectively, (p < 0.05), IgM-forming cells in bursa of Fabricus and spleen at the age of 7 days (p < 0.05) and IgG-forming cells in bursa of Fabricus at the age of 4 days (p < 0.05). In addition, CIAMP enhanced the IgA-forming cells in caecal tonsils diffuse area at day 4 (p < 0.05). Furthermore, CIAMP enhanced the antibody response to infectious bursal disease virus vaccine (IBDV) in chickens 21 days following IBDV vaccine administration (p < 0.05). These results suggested that CIAMP could modulate the humoral immune response of chickens and increased the antibody titres of infectious bursal disease virus vaccine.