A study was conducted to compare the effect of substituting synthetic DL-methionine (DL-Met) with herbal methionine (H-Met) as a natural substitute on some biochemical parameters and the humoral immune response of broiler breeder hens aged (50-55 weeks). 900 females and 108 males broiler breeders were distributed randomly into two groups, each group consists of 3 replicates, in three commercial modern opened houses. The birds were fed throughout the experiment on the two iso-energy, iso-crude protein diets according to nutritional requirements table of Ross-308. The difference between two diets was in the type of methionine added. DL-Met was added to the diets of group A at the rate of 1Kg/ton, while H-Met was added to the diets of group B instead of DL-Met at the same level for female broiler breeders. The results of the experiment cleared that there were no differences in production efficiency between the group containing DL-Met and other herbal alternative H-Met. The biochemical blood parameters were in the range of physiological values, and there was no significant (P>0.05) difference between the values of the group containing DL-Met and H-Met except the serum glucose value of H-Met which was higher significantly (P<0.05). As well as the antibody titers of ND before vaccination were significantly lower (P<0.05) than the antibody titers for experimental groups after vaccination at the end of the experiment. There were no significant (P>0.05) differences between the antibody titers of the group received DL-Met and herbal substitute H-Met. Results of the current study concluded that synthetic methionine DL-Met can be substituted with herbal substitute H-Met at the same rate without any adverse effects on the blood biochemical parameters or the humoral immune response to vaccination against Newcastle disease, as well as no negative effect of using H-Met on the productivity of broiler breeder. It is suggested that the effects of partial substitution of DL-Met with H-Met on the immune response of the broiler breeders should be studied more broadly in the future.