The original entrance doorway in that gable has been blocked, but its form is still legible, a round arch with a dropped keystone set beneath a hood-moulding of sandstone, with a wide round-arched window above it resting on a granite sill. These two phases of building, medieval and seventeenth-century, are now fused into a single fabric, surrounded by eighteenth and nineteenth-century memorials in the enclosed ground around them.

The site has been accumulating layers for well over a thousand years. Its earliest association is with St. Mochonna, a sixth-century figure connected to the early monastery of Hompatrick in Skerries, suggesting this was a place of religious significance long before any standing structure was raised. By the twelfth and thirteenth centuries the church of Carrickbrennan was held as a chapel by St. Mary's Abbey, the powerful Cistercian house in Dublin. After the dissolution of St. Mary's, the church and its tithes passed to Sir John Travers. The building that visitors see today owes its present form largely to Sir Edward Corker, who rebuilt the church for the parish in 1668, with further modifications following in the nineteenth century.

The site sits on flat ground and is straightforward to locate at the junction noted above. The walled graveyard encloses the structure, and the blocked west doorway and its stonework are visible from within the enclosure. The memorials in the surrounding ground span roughly two centuries and reward a slow circuit. Because the fabric of the building represents several distinct periods, including the possible echo of a sixth-century foundation, it is worth pausing at the west gable to read the layering of materials and phases rather than treating it as a single monument.