To investigate the prevalence and the risk factors of H9N2 avian influenza among backyard birds in Iran between October and November 2015. Methods: In this study, a total of 15 500 blood samples and 2 884 cloacal swab samples of backyard birds were collected in villages of Iran between October and November 2015. Then, serum samples were examined with the hemagluttination inhibition test and cloacal swab samples were pooled together and examined by RT-PCR. The samples that had serological titer ≥ 4 (log