Objective: 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 15500 blood samples and 2884 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 (log2) and villages that had at least one seropositive sample were considered positive. Results: Out of 559 villages, 526 (94.10％) were seropositive for the infection. Among 15500 serum samples, 7468 (48.18％) samples were seropositive for the infection. The seroprevalence according to species was 54.02％ among chickens, 17.59 ％ among ducks, 18.73％ among turkeys, 84.21％ among pigeons and 12.15％ among ostriches, partridges and pheasants. Based on molecular test, 3.04％ villages were positive. The seroprevalence in hot and humid area was less than that in cold and humid area (P<0.05). Conclusions: H9N2 avian influenza has high seroprevalence among backyard birds of Iran. Therefore, preventive measures such as biosecurity Practices and monitoring should be applied to reduce the prevalence.