Since its first detection in 1998, avian influenza virus (AIV) subtype H9N2 has been enzootic in Iran. To better understand the evolutionary history of H9N2 viruses in Iran, we sequenced 15 currently circulating H9N2 viruses from domestic poultry during 2017–2019 and performed phylogenetic analysis of complete genome sequences. Phylogenetic analyses indicated that the Iranian H9N2 viruses formed multiple well‐supported monophyletic groups within the G1‐lineage of H9N2 virus. Our analysis of viral population dynamics revealed an increase in genetic diversity until 2007, corresponding to the multiple introductions and diversification of H9N2 viruses into multiple genetic groups (named Iran 1–4 subgroups), followed by a sudden decrease after 2008. Only the Iran 4 subgroup has survived, expanded, and currently circulates in Iran. The H9N2 viruses possessed many molecular markers associated with …