During World War I, the brigade was formed as part of the First Australian Imperial Force in 1916, with the majority of its recruits coming from New South Wales.

It was assigned to the 3rd Division, and training was carried out in the United Kingdom before the brigade was committed to the fighting on the Western Front in November 1916.

During World War II, the brigade was mobilised for defensive duties, but did not see active service before it was disbanded in June 1944.

The brigade's constituent units were spread across various locations in New South Wales including Camperdown, Darlington, Enmore, Newtown, Marrickville, St Peters and Petersham.

Raised from volunteers drawn from New South Wales, the 9th Brigade was formed in 1916 in the period as the AIF was expanded following the failed Gallipoli Campaign.

Later in 1917, it fought during the Battle of Passchendaele before taking part in defensive operations during the German spring offensive in early 1918.

Following Japan's entry into the war, the brigade was called up for full time service and mobilised at Narellan before moving to Thornleigh, where it covered an area between Manly to Dee Why and Mona Vale.

[12] In late 1942, the brigade was warned out to deploy to Darwin, Northern Territory, but was instead moved to the Illawarra region.

Around this time, the brigade was tasked with vital asset protection in northern Australia, in the event of war.

[18] On 1 September 1994, the brigade moved from under command of Land Headquarters to form part of the 2nd Division, based in South Australia.