St David's Church is medieval in origin, and is depicted as St Arthen's church on historic Ordnance survey mapping. It is situated within a curvilinear churchyard, adjacent to the Afon Gwynon. The churchyard is enterd via a lychgate in its southern boundary, which borders the B4300. During the medieval period the church was a chapelry in the deanery of Stradtowy, and belonged to the Bishops of St David's as a prebend of the collegiate church at Brecon. In 1290 the prebend was appropraiated to the prior of the Knights Hospitaller by Bishop Beck. According to Lewis's Topographical Dictionary of Wales, in 1844 there were two chapels of ease to St David's Church. One was noted to be in ruins, and the other occupied by dissenters. Capel Herbach (NPRN 100629) is thought to be one of these chapels. A twelfth century wheel-cross, known as the 'Cross of Elmat', is built into the ground floor of the tower but is not in situ. It is thought to have been removed from nearby Cae'r Castell. Fragments of Early Christian Monument stones are thought to be built into the churchyard wall.

The church is a Grade II listed building, constructed of limestone and old red sandstone rubble. It consists of two-bayed chancel, three-bayed nave, south chapel, three-bayed south aisle with a three-storeyed west tower, and south boilerhouse. the plain, two-centred chancel arch is medieval in date. The nave is thought to be thirteenth-fourteenth century, as is the octagonal limestone font. The south aisle is thought to be fifteenth century. The tower is thought to date to the late fifteenth century, and its spiral stair is entered through a four-centred doorway in the west nave wall. The ground floor originally had a barrel-vault with segmental profile. The second storey has fifteenth century loops in its north, south and west walls. The belfry stage has cusped two-light openings in its north and west walls, and a single-light opening in its east. A large opening in the south wall is thought to date to 1826. The tower's parapet is crenellated and has a fifteenth century gargoyle. The chancel and south chapel date to the early sixteenth century. The building was restored in 1682, and the south chapel window may have been inserted at this time. The church was again restored in 1826, at which time the arcade was removed, the chapel arches blocked and the nave's east gable was rebuilt above eaves level. It was further restored in the late nineteenth century, at which time the brick boilerhouse was built. In 1906 a cross-incised broken stone formed the threshold of the church entrance. This is thought to possibly be represented by a stone fragment now in the chancel.

Sources include:
Cambria Archaeology, 2000, Carmarthenshire Churches, gazetteer, 48
www.genuki.org.uk/big/wal/CMN/Llanarthney

N Vousden, RCAHMW, 21 November 2012