What makes it particularly odd to look at is that the building carries two distinct architectural personalities at once: a roughly coursed limestone shell of medieval origin and a Classical doorway added in 1772, complete with an elaborate surround and a commemorative plaque above the west gable. The outline of the earlier west wall is still legible in the stonework, a kind of palimpsest left behind by the late eighteenth-century extension and refurbishment that pushed the building outward.

The documentary record reaches back to 1397, when a papal letter records Donatus Ofrarguil being appointed to the vicarage of a place rendered as 'Rathriebach', placing the site firmly within the machinery of late-medieval ecclesiastical administration. Two centuries of change followed: in 1594 the property passed to John Lye of Rathbride in County Kildare, and by 1607 it had been granted to Patrick Fox of Dublin. The Fox family connection is preserved inside the building itself, where an effigial tomb, that is, a tomb bearing a sculpted likeness of the deceased, commemorates Nathaniel Fox and is dated 1634. It rests against the north wall of the interior. The church also appears on two early maps: an early seventeenth-century map of Ardagh barony now held at the British Library, and the Down Survey map of Reathreagh parish from 1655 to 1656. The windows tell their own layered story; the three-light east window retains internal stonework that may date to the seventeenth century, while the external dressing is eighteenth-century work, and two twin-light windows survive in the south wall.

The church sits within the southern half of a graveyard, itself set on what was once demesne land, now given over to pasture. The effigial tomb of Nathaniel Fox and the visible seam between medieval fabric and Georgian intervention make the interior worth pausing over carefully.