The building itself is a layered thing: a tower added in 1760 onto a seventeenth-century structure, the whole then rebuilt in 1809, and now standing unused. What makes it genuinely curious is not what you can see but what almost certainly lies beneath it, and what was found nearby by a local man with a spade.

The parish church of Nenagh is traditionally attributed to St Colman and appears in written record as early as a deed dating to around 1217 to 1221, in which the advowson, meaning the right to appoint clergy to the living, was shared between the Butlers and the abbots of Abingdon in County Limerick. By 1615, a Royal Visitation was describing the church in bleak terms: 'ruynous, chancell downe'. The precise location of that medieval building has never been established. The Ordnance Survey letters, compiled in the nineteenth century, noted that 'not a vestige' of it remained, while speculating that the then-modern church had been built near or directly on its site. It was a local man, a Mr Rd. Burr of Nenagh, who brought the question closest to resolution. Digging at the rear of Barrack Street, about sixty paces north of the church and between it and the old abbey, he found foundation walls at a depth of roughly eighteen inches. The north and south walls ran about nine metres in length, were roughly six metres apart, and met at the east end in a curved wall forming less than a semicircle, a shape consistent with an apsidal chancel end. The stonework itself, walls up to one and a half metres thick, had already been entirely removed by the time the description was recorded. At the same spot, a bronze ring-seal was dug up. The graveyard attached to the present church retains a broken headstone dated to 1730, the earliest on record there, with a handful of other eighteenth-century stones among a majority from the nineteenth century.