St Mary's Church, formerly the parish church of Llanfair Orllwyn, is situated within a curvilinear churchyard, delineated by roads on its north-east and north-west sides. The churchyard sits at the centre of a network of roads and rights of way, one of which leads through the churchyard is depicted as circular on 1889 Ordnance Survey mapping, which also depicts a dwelling (with three small fields attached), Llanfair, adjacent to the southern churchyard boundary. It also depicts a parsonage, Persondy, immediately south of the road leading to the modern Old Rectory. The church was a parish church during the medieval period, belonging to the deanery of Sub-Aeron. It is thought to have been a possession of the Bishops of St Davids from an early date.

The form of the earlier church is not known. The font, whose square bowl has a chamfered underside rising to chamfered-off corners, is fourteenth century in date. The church was rebuilt either in 1808 or c1820, on the the same site and in the same locaton as its predecessor, possibly retaining some of the earlier fabric. Constructed of Ordovician shale rubble, it consists of two-bayed chancel, three-bayed nave and vestry (north of chancel east bay). It was not fitted out until 1842, by Rees Davies of Llandysul. The church was again restored and refitted in 1887, when the current roofs and floors were added and window frames inserted. The vestry also dates from this time.

Sources include:
Cadw, Listed Buildings Database

RCAHMW, 2 July 2014