St Luke's Church is depicted as St Llonio's Church on historic (1889-1905) Ordnance Survey mapping. A motte, Llanllwni Mount (NPRN 303828) is adjacent to the church, its western section ranging from 10-40m to the east and is partially obscurred by the churchyard to the west. The Jones Family Mausoleum (NPRN 418407) is sited in this area, and cists containing burials were encountered during its contruction. The Lloyd Family Mausoleum (NPRN 418406) is situated some 10m east of the church building.

The church is a Grade II listed building, considered to have strong external medieval character (provided by its sixteenth century tower) and good interior detail. It is constructed of local Silurian rubble stone, and consists of four-bayed nave, two-bayed chancel, four storeyed west towerand two-bayed transeptal vestry (north of tower). The medieval stone alter table was reinstated in 1917, after having been used as a seat outside the west door. There are three incised crosses visible on its surface, and measurements are given as 78in x 32in. The nave and chancel are thought to date to the thirteenth or fourteenth century, as is the square limestone font. A square, deeply splayed light in the north wall is medieval in date (unblocked in 1927), as is the square aumbrey. A narrow, two-centred doorway in the north wall formerly led to the rood stair. The tower was added in the early sixteenth century. A square spiral stair turret projects from the east half of the north wall. It is entered through a simple square sixteenth century doorway and lit by simple square slits (as are the tower's second and third storeys) of similar date. The tower's west door is two-centred and has a cusped two-light window above. The ground floor communicated with the nave via a plain two-centred arch, which is now blocked. A segmetal doorway and two-centred window, inserted through the blocking, are also thought to date to the sixteenth century. An inserted circular opening in the window blocking is thought to date to the nineeenth century. The belfry stage is lit by uncusped single light openings three with semicircular heads. There are known to have been two bells in 1552. By 1705 there was only one bell. The tower's parapet lies on an external corbel table. The church was restored in 1811, when the nave's south wall was rebuilt, removing a former south door. A west gallery was added in 1825. In 1827 a schoolhouse was built on the site of the present vestry. The nave was heightened in the later nineteenth centuryIn 1855 a fragment of carved alabaster, thought to represent an angel, was reportedly exhibited as having been found in the church. The church was again restored shortly before 1878, when the schoolhouse was removed and the vestry constucted in its place. The former rood loft stair was removed to facilitate this. The vestry has a blocked fireplace, with square chimney, in its north wall. The church was re-fenestrated, re-floored (with the addition of heating chamber and Porritt's stove) and is thought to have been re-roofed. The pews, stalls and wainscot dado also date to around this time. The church was again restored in 1934, in Arts and Crafts style, to the designs of W.E. Ellery Anderson, Cheltenham. The gallery was removed, the present roofs were installed, and the present finishes were added.

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

N Vousden, RCAHMW, 11 fenruary 2013