Its membership covers mariners as well as professional, administrative, supervisory and technical employees in the maritime industry and dependent services.

The National executive are: The AMOU is composed of two Divisions: "Offshore" and "Port Services".

The AMOU traces its roots to the formation of the Mercantile Marine Officers' Association in the 1880s.

The MMOA was one of the key unions involved in the 1890 Australian maritime dispute that began on 15 August 1890 and ended when members returned to work on the employers' terms in November 1890.

[2][3] A general meeting of the MMOA on 12 February 1904 changed the name of the union to Merchant Service Guild of Australasia.