All Saints Church is located in the centre of Llansaint, with several roads converging on it. The churchyard is curvilinear and is surrounded by roads on every side. A holy well, Ffynnon Saint ('saint's well') (NPRN 32249) is located some 300m to the north-east. Two early Christian inscribed stones were found within the church's wall fabric during the 1862 restoration, and were rebuilt into the south wall. The church is first mentioned in documents of 1115, at which time it was a chapelry belonging to St Ishmael's, which was to be granted to Sherborne abbey, Dorset. In 1141 it is thought that the churches were granted to Gloucester cathedral.The advowson of st Ishmael's and Llansaint was granted to the Bishop of st Davids by John of Gaunt in 1368. After the dissolution the advowson fell to the Crown. In 1833 Llansaint was a discharged vicarage in the patronage of the king, and a formal chapel of ease to St Ishmael's.

All Saints is a Grade II listed building. constructed of limestone, Old Red Sandstone and rubble stone, with yellow oolite dressings. It consists of a two-bayed chancel, three-bayed nave, single-bayed north transept, west tower, vestry (south of the chancel's west bay) and generator house(between the west vestry wall and nave). The nave and chancel are thought to be medieval. A blocked door in the has a medieval segmental head. A square recess in the east wall and a similar one beneath the south window may be medieval. The west tower dates from the late fifteenth century. it has three storeys and connects to the belfry via a stair set into the south wall, entered fron the churchyard. Two blocked windows, in the sanctuary north wall and the south wall, are thought to be seventeenth century. The building was restored in 1862, and the north transept and vestry date to this time. The west doors and chancel arch were rebuilt, and new windows were added. The church was also re-roofed, re-floored and re-seated. The oolite font is also thought to date to this restoration, as do the external oolite dressings. The generator house was constructed in 1927 of limestone blocks. The two uncusped double lancet windows inthe south wall of the nave are thought to date to 1937, rebuilt into 1862 openings. The sanctuary was polychrome tiled in 1934, and its steps were extended. The oak sanctuary dressings date from the 1950s. The plastered vestry ceiling is also thought to date to the twentieth century.

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

N Vousden, RCAHMW, 22 August 2012