Avian metapneumovirus (aMPV) is a major poultry viral pathogen that is increasingly gaining global attention due to its economic significance and widespread geographical distribution. The virus causes respiratory and reproductive infections in poultry and is associated with poor eggshell quality and a significant drop in egg production in laying birds. The first detection and report of aMPV was in South Africa in 1978 in turkeys. The virus has been detected in various poultry species including wild birds, has four well-characterized subtypes (A, B, C, D) plus two newly reported unclassified subtypes. To date, the well-known transmission route is via direct contact with infected birds or fomites, with wild birds heavily incriminated in viral spread in several studies. Although there seems to be no clear evidence of vertical transmission, horizontal transmission is greatly influenced by poultry stocking density on farms. Traditionally, immunological techniques have been used to demonstrate aMPV infections. Molecular tools such as polymerase chain reaction and sequencing are used to identify and characterize the virus. Virus isolation in cell culture is challenging, as primary virus isolation from clinical samples often requires multiple passages. In this chapter, we discuss the history, current epidemiology, transmission dynamics, pathogenesis, laboratory diagnosis, prevention, and control of the disease. We also highlight the need for biosecurity, enhanced global surveillance, and the application of molecular tools to track virus evolution and possible genetic mutations which may influence viral virulence, spread, and severity of infection among different avian species.