On the 10th November 1839 the first Church was officially opened. This building was to serve the Anglican community at Narellan until 1884 and became known as the School Church. Built by the Reverend Thomas Hassall it was used as a schoolroom on weekdays and a church on Sunday. The form of the 1839 building was a simple rectangle when built. It then had several additions made to it including the end bay with two gothic windows, the rendering to the walls to simulate stonework, a brick skillion wing to the west and an eastern verandah with closed end storerooms.

The various early improvements to the School Church were mostly made in the absence of Rev. Hassall. When he was present, it is clear from the Parish minutes that he had little time for Parish Council meetings and did not see a need for a more commodious church at Narellan. Instead it appears he concentrated his efforts on the Cobbitty Church.

All the while, the Parish of Narellan wanted to build a new church to house the growing population. The first subscriptions for the new church were taken at a parish council meeting on the 22nd April 1856, with most of the sizeable donations coming from the “Cobbitty Squires” Charles Cowper and John Oxley. Total promisaries from the meeting totalled £117.6.0 . A building committee was thus formed.

At a building committee meeting on the 20th September 1857, Reverend Hassall vetoed the plans for the new church and rejected all brickmaking tenders that had been received in his abscence. At his insistence it was moved all funds collected thus far should be applied to the “repair of the Church School House at Narellan and that Reverend T. Hassall be treasurer.” With the church funds safely in Reverend Hassall's hands there was no further discussion of a new church until 1868 after Hassall's death and the appointment of the new incumbent Reverend A.W. Pain. It was not until Rev. Pain took over the ministry that plans for a new church were taken seriously.

In April 1879 architect Edmund Blackett provided sketches of the new church. The sandstone structure would rival St Paul’s at Cobbitty, however a check of the building fund showed that the Parish could not afford to build the whole church entirely from sandstone so Mr Blackett was requested to amend his design and replace most of the sandstone with brickwork.

Although the church building was designed by Edmund Blackett in 1879 it was not finished until after his death. On Friday 30th May 1884 the foundation stone was laid by Miss Hassall, daughter of the first incumbent Rev Thomas Hassall. The church building was completed at the end of 1884 and was opened by Bishop Barry on the 16th of September of that same year. The church now faces Wilson Crescent but was designed to face Camden Valley Way, at the end of a planned - but not formed street named “Church Street”.

With considerable alterations to Blackett’s original plans the final cost of the new church was estimated at £1500.

In 1924 the church was completely renovated including interior painting, varnishing of the seats and new guttering and roof shingles. In 1926 the existing gas lights were changed to Aladdin mantle lamps. No further records for the church exist until 1959 and it is not known what works have taken place during that time.

By the early 1990’s both buildings were showing signs of wear and an application was made to the Anglican Church Property Trust to undertake major renovations of St Thomas’. In addition to this the parish council was once again raising the possibility of erecting a new church (on a new site) to meet the needs of the growing parish. In July 1995 repairs to the roof of both buildings and repairs to the windows were completed. In August the programme included the floor being infilled to form a continuous level floor.

The year 2000 saw the deconsecration of St Thomas’ when it was sold to private owners. With a name change to “The Old St Thomas Chapel” and substantial restoration, much has been done in order to breath life back into this historic site. Interior paint to match what is believed to be the original colour scheme, polishing part of the floorboards and repairs to the rooves and windows of both buildings have been undertaken.

With a plan of continued repair and restoration the new owners are gearing toward bringing The Old St Thomas Chapel to the forefront of the community once again.