The marble font was donated to St Peter's by Charles La Trobe in 1846 while he was still only Superintendent of the Port Phillip District, before he was appointed as the First Lieutenant Governor in 1851. The font came from an English church, but its age and earlier history are unknown. The mahogany cover on the font was designed by the architect Louis Williams.

The board on the wall behind the font is a memorial to Edward Cullingford, who went from St Peter's as a missionary to New Guinea, where he died in 1912. The memorial board originally listed the names of people who had gone from St Peter's to the New Guinea mission, but the purpose of the board was changed in 1993, when the centre panel became a memorial to La Trobe and the side panels became a list of parish incumbents. However, Edward Cullingford's name and memorial still heads the revised board.