St Lawrence's Church was a chapel of ease during the medieval period, belonging to St Martin's Church, Laugharne (NPRN 102141),as a perpetual curacy annexed to Laugharne Vicarage. By 1563 St Lawrences's Church, Marros (NPRN 413036) was also a chapel of ease to Laugharne parish, but both became a parish churches in 1769. In 1998 the church was a parish church, belonging to the Rural Deanery of St Clears. According to local tradition, the church was originally intended to be located in the field where the Giants Graves mound (NPRN 24423) is located, some 1.5km south-west. Howver, the stones placed there were mysteriously removed to the current church site. In 1898 excavations close to the churchyard walls reportedly uncovered thirty Bronze Age cremation urns. The base and shaft of a cross (NPRN 304162) survive within the churchyard. In 1880 it was noted that animals' heads (particularly wolves') were traditionally attcahed to the cross (as with other churchyard crosses), and that a few years previously a farmer from Marros had hung foxes heads on it. Another interesting feature is the churchyard boundary wall, noted in 1912, is the number of inscribed initials, each denoting the length of wall contributed by particular parishioners from 1786 to 1899.

The church is a Grade II listed building, constructed of limestone rubble. It consists of four-bayed nave and chancel, north transept (vestry), south porch and three-storeyed west tower. The cylindrical font's stem and base date to the thirteenth century, although its square bowl is of uncertain date. The nave and chancel are thought to date to the thirteenth-fourteenth century, and it is possible that the transept is of the same date. It is possible that the transept was originally an east to west running aisle. The porch may be fourteenth-fifteenth century. It has a plain, two-centred barrel-vault and two-centred door surround of Old Red Sandstone. The tower is thought to mainly date to the fifteenth century, with a window possibly dating to the sixteenth century, which is when the stair turret and parapet are to possibly have been added. The tower, which dwarfs the rest of the church, is noticably out of alignment with the nave. It is thought that the tower may have had a second building phase, possibly in the mid-sixteenth century, to which the west window, stair turret and crenellated parapet may belong.There is an early nineteenth century fireplace in the tower's first floor, where a school was held until 1840. The church was restored in 1844 (as commemorated on a plaque), when the tower's spiral staircase was blocked and a doorway was inserted in the west wall. The nave was reportedly substantially rebuilt, and the re-crenellation and heightening of the tower's parapet is thought to also date to this time. The church was again restored in 1895-1898, to the designs of Prothero and Phillott, Cheltenham, Cambridge and Newport. A trapdoor was inserted through the tower's vault. a wall was inserted between the north transept and the nave and chancel. The church was re-fenestrated, re-floored, re-seated and re-plastered. The stalls, pews and disused iron stove all date to this time, as does the masonry benching in the porch.

Sources include:
Cambria Archaeology, 2000, Carmarthenshire Churches, gazetteer, 48
Curtis, M, The Antiquities of Laugharne And Pendine And Their Neighbourhoods: Carmarthenshire, Amroth, Saundersfoot, Cilgetty, Pembrokeshire, South Wales (1880)

N Vousden, RCAHMW, 4 February 2013