The church that once stood on the north bank of the Dinin river, near its confluence with the Deen, has not simply fallen into ruin; it was largely consumed by the river itself. By 1839, when Ordnance Survey fieldworkers passed through and recorded what they found, the ruins and most of the associated burial ground had already been carried off by what they described as one of the frightful torrents to which the Dinin was liable. What remained of the graveyard was protected, just barely, by a stone wall on the river side. Today the church is not visible at ground level at all.

The site had been a functioning ecclesiastical place for centuries before the river took it. A church at Dysart, within the deanery of Ossory, appears in the taxation of the diocese of Ossory in 1312, suggesting an established parish with enough income to be worth recording. In 1392, a Robert Colkings held the position of vicar. By the mid-sixteenth century, Bishop John O'Tonory of Ossory, who held the see between 1554 and 1565, had appropriated the church, then referred to as "Desard-in-Dogh", to the Vicars Choral of St. Canice's Cathedral in Kilkenny. The Vicars Choral were a body of men attached to the cathedral whose role was to sing the liturgy; the income from appropriated churches helped support them. One further detail distinguishes Dysart's religious calendar: the local pattern day, a traditional gathering held in honour of a parish's founding saint, was observed not on the feast of the patron saint as was customary, but on the 29th of September, the dies dedicationis, the anniversary of the church's original dedication.