What makes this place quietly strange is the layering of it: a post-1700 Protestant church, itself long ruinous by 1840, almost certainly built over the footprint of a medieval Catholic parish church that had already vanished. When Ordnance Survey officers visited in 1840, they noted that the medieval church was "no longer in existence" and that its site was occupied by a small Protestant church already in ruins. A building replacing a lost building, and both now gone to decay.

The medieval parish church at Kilnarath appears in the ecclesiastical taxation of the Diocese of Cashel as early as 1302, suggesting an established parish presence here at least seven centuries ago. The Civil Survey of 1654 to 1656 still recorded a standing parish church on the land, referred to as "Killnyragh", and in 1652 a man named Cornelius Ryan was listed as its parish priest. The Church of Ireland building that replaced or overlaid it measures roughly 8.5 metres north to south and 21.6 metres east to west, with walls 0.75 metres thick, and contains two large barrel-vaulted mortuary vaults of nineteenth-century date; barrel vaulting in this context describes a curved stone ceiling formed like a half-cylinder, commonly used to roof burial chambers meant to last. The ivy that now smothers the walls prevents any further reading of the structure's details.

The graveyard surrounding the church is rectangular and contains headstones from the eighteenth and nineteenth centuries. Among them stands a holed upright stone that may have had a considerably earlier life: it has been tentatively identified as a medieval threshold stone, or possibly a socket stone, the kind of heavy block in which a timber door pivot would have turned. If that identification is correct, this unassuming piece of worked stone, now repurposed as a grave-marker, may be one of the few surviving fragments of the medieval church that once stood here before the centuries buried it.