St Simon and St Jude's Church, Llanddeusant, is sitauted within a curvilinear churchyard. During the medieval period the church was a chapelry belonging to the Deanery of Stradtowy. It was first mentioned in documents of 1282. The benefice is thought to have always been annexed to Llangadog vicarage, in the patronage of the Bishops of St Davids. The church became a parish church before 1833. The churchyard is bounded by roads on its east and south sides and a former road on its west side. The old Vicarage is immediately north of the churchyard, and it is also bounded on its north side by a former road. Historic (1887) Ordanance Survey mapping depicts a total of six roads converging on the church site. It is suggested that the original two saints of the parish name were Potolius and Notolius, sons of a local saint.

The church consists of four-bayed nave and chancel, four-bayed south aisle (same dimensions as nave and chancel), west porch/two-storeyed bell turret (against south aisle west wall). The church is a Grade II* listed building, constructed of limestone rubble with some Old Red Sandstone. The octagonal conglomerate font font bowl is thought to be fourteenth-century in date. The south aisle was formerly the nave and chancel, and is thought to date to the fourteenth century. The nave and chanecl was formerly the north aisle, and is thought to date to the fifteenth century. In 1659 it was noted that the interior walls had been prepared for the painting of the Royal Arms, Decalogue and Creed. In the nineteenth century there was more than one bell present. By 1827 the chancel was in the north aisle and the church was whitewashed inside and out. In 1830 the bell turret was partially rebuilt. The church was restored in 1885, when the floor level was raised to accomodate heating apparatus. The nave and south aisle passages were flagged with limestone, and the church was reseated. The south aisle east bay was converted to a vestry withh oolite fireplace. The church was again restored in 1913-1914. The nave and aisle side windows are thought to have been rebuilt in oolite. The porch/bell turret openings were also largely rebuilt, and the chancel floor is thought to have been tiled. The alter rail and pulpit are also thought to have been added at this time. The octagonal oolite font stem and base date to the twentieth century. Restoration work was undertaken in 1987-1988, when the roof timbers were renovated and the interior walls were repointed and roughcasted.

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

RCAHMW 2021