St Cynwyl's Church is situated within a curvilinear churchyard (formerly circular), bounded by the Afon Duad on its east side. During the medieval period the church was a chapelry appended to St Lucia's Church, Abernant (NPRN 301841) in the Deanery of Carmarthen. In 1197 the parish and chapelry were illegally granted to Carmarthen Priory by William de Braose. In 1284 they were granted to Carmarthen priory by Maradudd ap Rhys Maredudd. In 1290 the grant was confirmed by Bishop Bek of St Davids. By 1720 St Cynwyl's was the parish church of Cynwyl Elfed. In 1833 the living was annexed to the vicarage of Abernant.

The church is a Grade II* listed building constructed of local rubblestone with limestone (from around 1600) and yellow oolite (from 1863) dressings. It consists of two-bayed chancel, three-bayed nave, three-bayed north aisle, west porch, bellcote and coalhouse north of the north aisle west bay. The nave and chancel are thought to date from the the thirteenth-fourteenth century. The nave's (internal) north wall has a low butress built against it, which supports a re-set medieval stoup. The chancel east window is of three-lights in a square surround and is thought to date from around 1600. A blocked four-centred doorway is thought to date to the same time. The north aisle is thought to date to around 1500, and is seperated from the nave and chancel by a three-bayed arcade consisting of segmental arches on octagonal piers. The church was re-fenestrated around 1600. The west porch was added in the early nineteenth century, and was constructed of brick. It was extended to the west when the church was restored in 1863, and the north wall brickwork was replaced by a window. The church was restored in 1863, at which time the porch was extended. The coalhouse was added around 1900. The church was again restored in the early-mid twentieth century, when the chancel was refloored and its south door blocked.

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

N Vousden, RCAHMW, 17 December 2012