Dexamethasone is one of the strong synthetic steroids. It has a multipotent effect on the body's cells and tissues, including the immune system, as it induces immune suppression, but sometimes can modulate the immune response, which is still vague and unclear. Although the poverty of studies about their action when administered in parallel with the vaccination program. We aimed to use poultry as a model to study the effect of dexamethasone administration in parallel with the infectious bronchitis vaccination regime. Sixty one-day-old chicks were divided into four groups; the first group was treated with a full dose of dexamethasone ED100 with infectious bronchitis vaccine, while the second group was treated with ED50 of the drug with IB vaccination, whereas the third group was used as a positive control treated with the IB vaccine, and the fourth group was used as a negative control kept without vaccination. The ELISA test was used to detect antibodies against infectious bronchitis as a result of vaccination, and levels of CD4 and CD8 T-cells as indications for the effect of dexamethasone on vaccination.  Results showed that the low dose of dexamethasone (ED50) provided a significant increase in antibodies against infectious bronchitis, with an increase in the levels of CD4 and CD8 compared to the others. We conclude that a low dose of dexamethasone may positively affect the immune response to the vaccination program when administered with the infectious bronchitis vaccine.