The site of Capel Mair lies within the village of Pencader (NPRN 96648), some 50m north-west of medieval motte and bailey, Castell Pencader (NPRN 303809). The site is now occupied by St Mary's Church (NPRN 418670). During the post conquest period Capel Mair was a chapelry, with burial rights, belonging to Llanfihangel ar arth, in the Deanery of Carmarthen. A spring is depicted on historic (1889 and 1906) Ordnance Survey mapping, some 20m north-east of the church. The spring does not appear on modern Ordnance Survey mapping, which depicts a buiding some 40m south (also depicted on historic mapping, and linked to the spring by a footpath) as 'Ffynnon-fair'. This may reflect the historic name of the spring. 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 Church. The church's limestone font and cylindrical stem (constructed from one piece of stone) is thought to date to the thirteenth-fourteenth century.

In 1710 the church was noted to be ruined, with most of the stone having been removed and used to construct a meeting house just beyond the churchyard. Yr Hen Gapel, established in the 1670s, is situated some 170m south-east of Capel Mair (now St Mary's Church). Yr Hen Capel may be the chapel referred to in 1710 as probably having been built with stone from the ruined Capel Mair. The current St Mary's Church (NPRN 418670) was erected in 1881 on the same site, and probably in the same location. Capel Mair's font was brought from St Michael's Church, Llanfihangel-ar-arth (NPRN 101772).

Sources include:
Cambria Archaeology, 2000, Carmarthenshire Churches, gazetteer, 48
Ordnance Survey, 1889, first edition 25in
Ordnance survey, 1906, second edition 25in
Ordnance Survey, modern Mastermap, 1:10,000

N Vousden, RCAHMW, 24 September 2012