The building sits within a graveyard in a fairly advanced state of collapse, its east gable entirely gone and a section of the north wall lost near the west end. What remains still reads as a substantial structure: a rectangular nave measuring 21.5 metres by 6.6 metres externally, with walls just over a metre thick, and a doorway on the south wall positioned 4 metres from the west gable, standing 2.5 metres high and a metre wide. That doorway, carefully proportioned and still legible amid the general decay, gives some sense of what the building once was before the ivy and the centuries took over.

The church is recorded under the name Killahan, and its dimensions suggest a building of some local ambition. The thick walls point to construction intended to endure, though the dedication and precise date of foundation are not currently recorded. Just across the road to the west stands a separate and easily missed monument, the stone cross of Tonaknock, making this small roadside area something of an informal cluster of early ecclesiastical remains in the North Kerry landscape. The church and cross were documented as part of the North Kerry Archaeological Survey, published in 1995 by C. Toal, which catalogued the remarkable density of early medieval and later religious sites across this part of the county.