Background: The H9N2 subtype of influenza A viruses is considered to be widespread in poultry industry. Adamantane is a group of antiviral agents which is effective both in prevention and treatment of influenza A virus infections. These drugs inhibit M2 protein ion channel which has role on viral replication. OBJECTIVES: The main objective of this study is to evaluate M gene of avian influenza viruses (AIVs) of H9N2 subtype in order to find adamantane drug resistance mutations. METHODS: Over 100 suspected samples were collected from different geographical regions of Iran during 2012-2013. Samples were injected via allantoic sac of 9-11 day-old chicken embryos. A total of 11 out of 100 were AIV. The H9N2 subtype was confirmed by specific RT-PCR. The RT-PCR was conducted for full length M gene. PCR amplified products were purified and then conducted for commercial direct sequencing. Finally, sequences were checked for possible sites of adamantane resistance mutations. RESULTS: Overall, 8 out of 11 viruses harbored the adamantane resistance-associated mutations. Of which, four viruses were isolated in 2013 and four viruses in 2012. Two different resistance-associated mutations were observed during different years. CONCLUSIONS: The present study provided clear evidence concerning resistance AIVs of H9N2 subtype that were circulating in Iranian poultry sector. This concern is always present as M segment might be introduced into human influenza viruses by reassortment phenomenon.