St Brynach's Church is medieval in origin, and belonged to the medieval deanery of Carmarthen. It was subsequently appropriated by the Cistercians of Talley Abbey, and later became the property of the Bishops of St Davids as a prebend of the collegiate church, St David's (NPRN 96671) at Llanddewi Brefi. It is situated within a curvilinear churchyard, with the road dilineating its west and south boundaries. The church is some 220m north-west of motte and bailey castle, Castell Mawr (NPRN 304225). A seventh-eighth inscribed stone built into the south door blocking has a Latin inscription. Another inscribed stone, also with a Latin inscription, was reported in 1746. A third stone, also thought to bear the remnants of a Latin inscription, was reported in the churchyard in 1875 but could not be located a few years later.

The church is constructed of rubble stone with Bath stone dressings and slate roofs with crested ridge tiles, coped gables and cross finials. It is cruciform in plan and consists of three-bayed nave, three-bayed chancel, two-bayed vestry, north and south transepts, west porch and west bellcote. The nave is thought to date to the thirteenth century. The north transept is thought to date to the early fourteenth century, and the south transept to the late fourteenth century. The chancel is thought to date to the fifteenth century, as did the former west tower, which collapsed around 1725. There were repairs in 1826, which may be when the west wall was rebuilt. The chancel was restored around 1845 and a gallery was inserted in the nave. In the 1850s the church was re-fenestrated, re-roofed and re-floored and the bellcote was added. There is a south transept window of 1849 by Bell of Bristol which is one of the earlier pieces of stained glass in the region. The church was restored in 1878 by George Morgan, at which time the vestry and porch were added. There are two heraldic shields (upside down) in the east wall. The octagonal, oolite font dates to the late nineteenth or twentieth century.

Sources include:
Cadw, Listed Buildings Database.
Cambria Archaeology, 2000, Carmarthenshire Churches, gazetteer, 48

RCAHMW, 22 November 2012