In 1884 Thomas Chirnside of Werribee Park erected the bluestone St Thomas's Presbyterian Church and manse on his own land at Werribee. The entire cost of the construction of the two buildings, ₤3500 was paid by Chirnside.
Messrs Harding and Holyoak of Geelong built the church and manse designed by the eminent Geelong and western district architect Alexander Davidson.
The church is the last of a small number of churches designed by Davidson and his partner George Henderson in the French Gothic mode which they favoured. It features a distinctive octagonal tower with engaged colonettes and a stone spire. The initials TC form part of the design of an iron weathervane at the top of the spire. The interior of the church is notable for its timber ceiling and roof trusses decorated with carved eagles, the Chirnside family emblem. In this respect the interior resembles the billiard room addition built in 1883 at Werribee Park and also designed by Davidson.
In 1897 George Chirnside (a nephew of Thomas Chirnside) had a family pew made for the church. Originally containing six seats the elaborately carved English oak pew was raised and enlarged in 1956 to accommodate the choir.
The bluestone manse is a highly intact single storey domestic building with double gable ends and fretwork bargeboards to the street elevation. The front verandah features the distinctive patent case iron details which were characteristic of the work of Davidson and Henderson. The verandah columns and decorative cast iron brackets are identical in pattern to those at Narrapumelap homestead, Wickliffe, designed by Davidson and Henderson in 1872.
St Thomas's church and manse are together an important part of the built evidence of the Chirnside association with the Werribee area, Werribee Park and Point Cook. These two buildings and the land are illustrative of the patronage by which Thomas Chirnside sought to recreate in Werribee the way of life of an English country gentleman.