St Deiniol's Church, Llanddeiniol, is situated within a curvilinear churchyard, some 20m south of a waterway which converges with the Afon Carrog some 170m further south-east. The church was a parish church during the medieval period, belonging to the Deanery of Ultra-Aeron. At that time it was a prebend of the collegiate Church of St David's, Llanddewi Brefi (NPRN 96671). The patronage subsequently fell into private hands and in 1833 the living was a perpetual curacy in the patronage of the Price family.

The medieval church consisted of nave and chancel divided by a double timber rood screen. The screen reportedly still bore paintwork and featured depressed two-centred arches with a gallery above carrying heraldic devices.The rood-screen was reportedly painted in large lozenges, with quarterly argent & gules with a star gules in the first and third quarters. On one pillar of the screen was an 'ancient painting of a man's head'. The church's thatched roof was replaced with tiles in 1785. The church's present font is thought to be thirteenth-fourteenth-century in date. In 1783 the vestry minute book noted repairs made to 'the chest that keeps the bones' and in 1787 it was noted that it was agreed to 'dig a place to bury the bones'. This signifies the presence of a saint's relic.

The church was entirely rebuilt in 1835 on the same site and in the same location as its predecessor. The current church is a Grade II listed building, constructed of local silurian rubble stone with yellow oolite dressings. It consists of three-bayed nave and apsidal chancel (above crypt) and three-storeyed west tower. In 1881 the church consisted of the present nave and tower and a small, square chancel (above crypt). At that time the church was lit by three Y-traceried windows. The church was restored in 1883, to the designs of Middleton and Son, Westminster and Cheltenham. All openings (except in the belfry) were rebuilt and the church was reroofed and refloored. The chancel was demolished and replaced with the present apse. The crypt was also rebuilt, reportedly to accomodate biers.

Sources include:
Cambria Archaeology, 2000, Ceredigion Churches, gazetteer, 48
Eyre-Evans, G., 1903, Cardiganshire and its Antiquities
Richard Suggett, Painted Temples: Wallpaintings and Rood-screens in Welsh Churches, 1200–1800, (RCAHMW 2021), pp. 52.

RCAHMW 2021