Avian metapneumovirus (aMPV) causes one of the most prevalent diseases of poultry mainly in combination with other pathogens, and it is increasing among chickens.  In the present study, the detection and characterisation of an aMPV subtype B strain circulating in broiler flocks based on fusion (F) gene. In phylogenetic analysis, the isolates are located in B subtype cluster and near aMPV strains from Russia (99.58%). It is the first molecular characterisation based on F gene of aMPV in Iran. It is also concluded that more work is required to isolate and characterize aMPV in different geographical regions of Iran and several species.