A baptismal font is the vessel used to hold water for the rite of baptism, and its placement at the entrance to the nave carries deliberate theological meaning, marking the threshold between the secular world and the sacred interior. This one measures roughly three quarters of a metre across and just under half a metre in depth, with rounded corners softening what would otherwise be a very angular block of stone.

The basin at its centre is circular, around half a metre in diameter and just over a quarter of a metre deep, and it retains a central drain-hole, the small opening through which water used in the baptismal rite would have been directed rather than simply left to stagnate. Granite is a durable, coarse-grained stone common to Wicklow, and its use here gives the font a solidity that suggests it was built to last rather than to impress. When the font was inspected in 1990, it remained in its position immediately inside the nave door of the associated church at Kilcoole.