St Cyndeyrn's Church was a parish church of the medieval Deanery of Kidwelly. In 1355-1356 the church, along with the chapels Capel Dyddgen (NPRN 303927) and 'Llangenhython', was granted to New College, Leicester. The parish of Llangyndeyrn is also noted to have had two other medieval chapelries. the advowson is thought to have always belonged to the Lord of Kidwelly. The churchyard is curvilinear, and the base of a medieval cross (NPRN 303925) is located to the south-east of the church.

The church is a Grade II* listed building, constructed of rubblestone. It consists of two-bayed chancel (with square projection for former rood stair), three-bayed nave, three bayed north aisle, two-bayed north chapel, south porch and three-storeyed west tower. The nave and chancel are thought to be thirteenth-fourteenth century. The tower's lower storey was formerly a porch, and dates to the early fifteenth century. The north chapel and current porch date to the late fifteenth century. It is lit by two two-light windows in its north wall dating from 1883-1888, and floored with re-used seventeenth-eighteenth century memorial slabs. The tower's upper storeys, and the north aisle date to the sixteenth century. The tower as a whole is atypical of the region, and is described as tall, narrow and tapering. A low panelled screen between the chancel and north chapel dates to 1676. The church's three bells were replaced in 1679. Two of the current bells date to this time, and one from 1721. The church is thought to have had former components to the west of the north aisle (detactched from tower), south of the nave west bay (detatched from porch)and on the site of the present boilerhouse. The components are thought to have been post-medieval, and were removed during either a restoration of the late 1850s or the 1883-1888 restoration (to the designs of architect J.P St Aubyn). The floors were lowered at this time, and 497 skeletons were unearthed. The church was also re-roofed (retaining some earlier timbers), re-floored and re-fenestrated. and the chancel's east gable was rebuilt. The marble font dates to the early twentieth century. The boilerhouse dates to 1927. The church, particularly its seating, was renovated in 1935.

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

N Vousden, RCAHMW, 10 December 2012