By far the largest military complex, St Andrew's Barracks were the result of progress in the design of garrison towns.

Designed by the Royal Engineers, plans for the building of St Andrew's Barracks were started in the 1890s, the first stone laid in 1901 and buildings were still being erected until the late 1920s.

The new barracks were aimed to accommodate at least 1,000 infantrymen, their officers and spouses. They consist of single and married soldiers' accommodation, single and married officers' quarters, transport depots, recreational facilities, schools, stables, churches and all other ancillary facilities required by the military.

The guard room with its prominent clock tower were built in 1903 and the Army Children's School in 1908. They were followed by Juno House, a large officers' mess and single officers' quarters. The gymnasium was built in 1912, along with the medical centre and Christ's Church and Australia Hall in 1915. In 1921 the NAAFI was established and was given its own building, until St Andrew's Barracks were furnished with buildings to meet most requirements by a garrison of this size.

Improvements and other buildings such as administrative blocks and workshops were added in time, even as late as the 1960s. In 1978 St Andrew's Barracks were closed down and ceded to the Maltese government in preparation for the withdrawal of all British forces in 1979.

In 1996 Mepa scheduled about 50 properties of St Andrew's Barracks ranging from Grade 1 to Grade 3 buildings of historic, architectural and contextual value as they form part of a larger already-scheduled military complex. They were republished following a revision as per Government Notice number 880/09 dated October 30, 2009.