The current St Mary's Church is thought to have been built on the same site and location as medieval Capel Mair. St Mary's church is situated in the village of Pencader (NPRN 96648), some 50m north-west of medieval motte and bailey, Castell Pencader (NPRN 303809). During the post conquest period Capel Mair was a chapelry, with burial rights, belonging to St Michael's Church, Llanfihangel-ar-arth (NPRN101772), in the Deanery of Carmarthen. In 1828 a stone was reortedly found near the church, bearing a Latin and Ogham inscription. A copy of the Latin inscription has been translated as 'DECABER BALOM FILIVS BROCAGNI', and the Ogham as 'DECCAIBAR BROCAGNI'. The stone was reportedly broken to pieces before 1855, by a farmer who objected to people trespassing on his land to see it. In 1912 a few fragments of the stone, two bearing Ogham characters, were kept in a box in the vestry of St Mary's.

The church's limestone font and cylindrical stem (constructed from one piece of stone) is thought to date to the thirteenth-fourteenth century. It is reportedly derived from Capel Mair, although it lay in the churchyard at Llanfihangel-ar-arth until around 1881. The current building was erected in 1881, and licenced for use in 1882. It is constructed of shaley slate rubble, and consists of three-bayed nave, two-bayed chancel, south porch, north vestry and single west bellcote. The vestry has a lean-to roof. All openings date from 1883. They are neo-gothic with lancets, constucted of yellow oolite.

Sources include:
Cambria Archaeology, 2000, Carmarthenshire Churches, gazetteer, 48

N Vousden, RCAHMW, 25 March 2013