The Municipal Officers' Association of Australia was formed in 1920 and was registered in 1921. It grew from a small and politically conservative union into a large and more vocal organisation. In 1991 it amalgamated with the Australian Transport Officers' Federation and the Technical Service Guild of Australia to form the Australian Municipal Transport Energy Water Ports Community and Information Services Union. After amalgamations with other unions in 1993, it changed its name to the Australian Municipal Administrative Clerical and Services Union, known as the Australian Services Union.

The Technical Service Guild was formerly the National Service Guild, an in-house state-registered staff organisation within the company NCR. Registration of a union to represent employees in the business equipment, electronics and newly developing computer industry came about in 1970 as a result of the deterioration of conditions in the industry in the late 1960s. In its early years, the Technical Service Guild worked to establish a Federal Award which it gained in 1971, amid the fiercely anti-union sentiment of large employer groups in the industry. Over the next few years the Guild established branches in most states, and despite its scarce resources continued to organise and protect workers in what has now become the information technology field. The union finally merged with the Municipal Officers' Association of Australia and the Australian Transport Officers' Federation to form the Australian Municipal Transport Energy Water Ports Community and Information Services Union in 1991. After further amalgamations in 1992 and 1993, it became the Australian Municipal Administrative Clerical and Services Union, known as the Australian Services Union.

Formed originally in 1942 as the Australian Shipping Officers' Association, the union changed names in 1988 to the Australian Shipping and Travel Officers' Association. In 1993 it amalgamated with the Australian Municipal Transport Energy Water Ports Community and Information Service Union, which after further amalgamations later that year became the Australian Municipal Administrative Clerical and Services Union, known as the Australian Services Union.

The union known as the Australian Services Union began in 1991 as an amalgamation of the Technical Service Guild of Australia, the Municipal Officers' Association of Australia and the Australian Transport Officers' Federation and took the name the Australian Municipal Transport Energy Water Ports Community and Information Services Union. It retained this name after amalgamation with the Australian Social Welfare Union and the Western Australian Railway Officers' Association in 1992 and with the Australian Shipping and Travel Officers' Association in 1993, but changed its name to the Australian Municipal Administrative Clerical and Services Union later in 1993 after amalgamation with the Federated Clerks' Union of Australia and the Federated Municipal and Shire Council Employees' Union of Australia. In 1994, the Totalisator Employees' Association of Victoria was incorporated in the union.