Holy Trinity Church was established in 1836 as the Pioneer Church for the new colony of South Australia and is closely associated with the early history of the state.

The Revd Charles Howard, an Irishman from the Diocese of Chester, travelled to South Australia on HMS Buffalo and commenced duties as the first Anglican minister. He brought a prefabricated church building funded by the South Australian Church Society, but having suffered damage on the voyage, it was useless. He had to use temporary facilities for some time.

The Society received the right to a Town Acre from Mr Grenfell. The Trustees appointed by the Society arranged for Col William Light, the colony’s Surveyor General, to choose the location for the church building. Acre No.9 was originally near the main river crossing and beside the main road to the Port.

The foundation stone of the permanent building was laid by Capt John Hindmarsh, South Australia’s first governor on 26 January 1838. The bulding was rebuilt in 1845, and significantly extended in 1888-9, when it was transformed to its existing Victorian Gothic style. Pointed windows were installed, a pitched roof with fine timber trusses replaced the original flat roof, supported by masonry buttresses and higher walls, while the tower was extended to its present height. Twentieth century additions include galleries, the organ loft, and extra vestry space.

The site also includes a Rectory (built in 1851, now offices), a Parish Hall (added in 1887), a smaller hall, offices, a crèche, a cottage (now meeting rooms) and a large car park.

The church building is on the Register of the National Estate.  It is also, along with the Parish hall and Rectory, on the State Heritage list.

In 2001 Trinity planted Trinity Hills, a congregation in Aldgate and in 2006 planted Trinity Bay at Hove.  A paper on the Trinity Hills church plant is available to download.

Trinity North East was planted in 2010, a week before TMB, and in February 2013, Trinity Inner South was launched.

In 2015, Trinity Mount Barker's "South Coast Studies" Bible Study Groups, youth group and kids' program grew into a new church, Trinity South Coast.