An understanding of the development of the chicken immune system from early embryogenesis is important for developing new strategies for improved poultry health. Typical findings show that large developmental changes occur immediately post-hatch, however, less information is known about changes that occur early in embryogenesis. Furthermore, immune competence may be tissue-specific as well as age-specific, and as such it is important to analyze its development within specific tissues. The chicken chorioallantoic membrane (CAM) is a highly vascularized extraembryonic membrane which performs multiple functions during embryonic development, including immune protection. As the immune response is key to early management and control of infections, knowledge of the age that this response mechanism develops is important for developing novel approaches for enhanced poultry health. Following completion of a number of in ovo vaccine virus inoculations, we have confirmed that viral infection occurs within the chick CAM. Following infection, we have observed the generation of a variety of antiviral immune response elements within the CAM, through the upregulation of interferons and interferon-stimulated genes. These results support further investigations into the role of the CAM as a means of protection for the developing embryo. Knowledge of the expression levels of these systems throughout embryogenesis may help to understand age-related susceptibility to viral infection, and may be of further interest for understanding the relative effectiveness of pre-natal and early vaccination of chicks.