In 1835, the Western Australian Missionary Society, a society formed in Dublin and London in part by Colonel
Frederick Irwin, appointed Giustiniani to establish a mission in the Swan River Colony,
Western Australia. Giustiniani was from the noble Italian Giustiniani family, one of the princes of which had married into an English family, and Louis was connected to the heirs of the estate and title of Earl of Newburgh. He was Catholic by upbringing but had renounced the Catholic faith. His mission was to "civilise" and
Christianise the Aboriginal people, and to learn their language. His response included the statement that the settlers "stand nearly as much in need of religious instruction as the" Aboriginal people. This statement resulted in numerous letters to the Perth Gazette, particularly on the part of "A Publican", criticising his "excess of zeal". Giustiniani visited
York in September 1836 and preached the first sermon in the York district, at
Joseph Hardey’s and then at
Rivett Henry Bland’s. He promised to visit every seventh week. This visit coincided with the murder of an Aboriginal person who was taking flour from a barn, by Ned Gallop, at the direction of his employer
Arthur Trimmer, which Giustiniani investigated. Governor
Stirling gave Giustiniani a parcel of his own land at Woodbridge,
Guildford, upon which to start a mission and school, which he intended to be along Moravian lines. His wife was probably a member of the
Moravian Church. He succeeded in constructing a church which was situated approximately where the
Guildford Grammar School Chapel now stands. ==Defence of Aboriginal people ==