Highly pathogenic avian influenza virus (HPAIV) H5N1 is an endemic disease in Egypt and severe outbreaks have been reported even in vaccinated flocks. Several H5 vaccines have failed to protect birds against Egyptian H5N1 virus. In this study, the antiviral effect of green tea extract (GTE) in combination with inactivated H5N1 vaccine was evaluated. GTE found to be safe at high concentration on Vero cells and decrease the CPE on infected cells. In vivo, specific pathogen free chickens were allocated into four groups, 15 birds each. Negative control group, positive control group, vaccinated group, vaccinated group supplied by GTE in drinking water (5gm/L). Blood samples were collected weekly and tested using (HI) test. Lung tissue specimens collected for histopathology and immunohistochemistry. Interestingly, vaccinated non-treated birds exhibited severe post vaccinal reaction and deaths. GTE in combination with inactivated vaccine increased HI titer one-week post vaccination, and no deaths were recorded in this group. Moreover, treated chickens did not excrete virus in swab samples and minimal antigen and pathological changes were reported in its lungs. The addition of GTE prevent the shedding of the virus and achieve complete protection against HPAI.