St Illtyd's Church, Pembrey, was a parish church during the medieval period, belonging to the Deqanery of Kidwelly. In 1120 it was granted to the Benedictines of Sherborne Abbey (Dorset), by Roger of Salisbury (Lord of Kidwelly). In 1353 Henry, Duke of Lancaster and the Bishop of st Davids granted the church, along with its two chapelrys, Llandury and Llancommowr, to the New College of Leicester. In 1366 the church was granted by the Bishop by John of Gaunt (Duke of Lancaster) to the Bishop of St Davids, on the condition that a chantry be founded within the church (to which the revenues of St Ishmael's church were appropraited). After the dissolution the advowson fell to the Crown, but subsequently found its way into private patronage. In 1853 it was in the patronage of the Earl of Ashburnham. This was purchased by the Elkington brothers in 1880, who later presented it to the Ecclesiastical Commission. In 1998 the church was a parish church.

The church is a Grade I listed building, constructed of local rubble stone. It consists of three-bayed nave, lower and narrower two-bayed chancel, north aisle, two-bayed north chapel, four-storeyed north-west tower, south porch, toilet block (north of tower) and below-ground boilerhouse. The nave is thought to date to the thirteenth century, and has a three-light Perpendicular west window, beneath the sill of which are embedded stone uprights defining an earlier west doorway. The chapel is thought to date to the fourteenth century (possibly a chantry chapel dating from the 1366 grant to the Bishop by John of Gaunt). The chancel is thought to have been rebuilt at this time. Its east bay south wall features a plain, two-centred aumbry and a crude, square piscina bowl. The porch, thought to date to the fifteenth century, has double boarded doors to a pointed doorway, above which is a re-set sundial with gnomon, and a plate dated 1773 by David Thomas. It also records Morgan Morgan and Thomas John as churchwardens. The north aisle and tower (three storeys) date to the sixteenth century. On the tower's west face is a doorway with Tudor arch and continuous chamfer, leading to a door with vertical ribs. The second stage has a narrow window with round clock face above, to west, south and north faces (inserted in 1935-1936). A large window in the nave south wall dates to the sixteenth century (largely reset in 1910-1911). A possible earlier tomb recess descends nearly to floor level below it. The church was restored in 1856-1857. The chancel's two-light south wall windows may date to this time. Between them is a memorial slab commemorating the dead of three nineteenth century shipwrecks on Cefn Sidan Sands. These were the French vessel La Jeune Emma (NPRN 240649) in 1828 (one of whose victims was Adeline Coquelin, niece of Napoleon's consort Josephine), Brothers (NPRN 273864) of Liverpool in 1833 and Pickering Dodge (NPRN 274056) of the USA, in 1839. The church was again restored in 1910-1911, when the boilerhouse was added and the sanctuary and passage floors were replaced. A priest's door in the chancel west bay was blocked at this time, and the tower's fourth storey was added. The toilet block dates to the later twentieth century. There is an eighteenth century benefaction board and inscriptions.

Sources include:
Cadw, Listed Buildings Database
Cambria Archaeology, 2000, Carmarthenshire Churches, gazetteer, 48
Richard Suggett, Painted Temples: Wallpaintings and Rood-screens in Welsh Churches, 1200–1800, (RCAHMW 2021)

RCAHMW 2022