St Cathen's Church is situated within a curvilinear churchyard in the centre of Llangathen, some 250m west-north-west of Aberglasney House (NPRN 17068). Historic (1887 and 1906) Ordnance Survey mapping depicts a vicarge immmediately north-east of churchyard, with a pub immediately north-west. The land on which these three properties are situated (an inverted 'C' shape) is dilineated to the north and east by two roads and the junction at which they meet. 1.8km south of St Cathen's is the site of a a well or spring (NPRN 32248) reportedly depicted on the 1840s Tithe map as Ffynnon Cathen. St Cathen's was a post-conquest parish church, of the medieval deanary of Stradtowy, and was a possession of the Prioress and nuns of Chester. It had at least two dependent chapelries.

The church is a Grade II listed building, constructed of limestone rubble with limestone (seventeenth century), yellow oolite (1868) and red sandstone (1899) dressings. It consists of three-bayed chancel, three-bayed nave, three-bayed south chapel, north transept, three-bayed south aisle, south porch, three-storeyed west tower and coalhouse. The nave and chancel are thought to date to the thirteenth century. The north and former south transept (now absorbed by the south aisle) date to the fourteenth century. The tower is thought to be early fifteenth century. It has a spiral stair turret, similar to that at St Egwad's Church, Llanfynydd (NPRN 301832). The turret is entered through an early fifteenth century doorway with a two-centred head. The stair is lit by simple square lights to first storey, simple light to the second, and plain and cusped lights to the third. The parapet is crenellated. The south chapel, known as the Aberglasney chapel, dates to around 1600 and belongs to the Aberglasney estate. It was added as a mortuary chapel for Bishop Rudd, former occupant of Aberglasney. The south aisle dates to the early seventeenth century. The alter rails are thought to date to the early seventeenth century (in 1956 it was noted that, in 1867 a tudor alter and alter rails originally belonging to St Bennet's Church, Gracechurch St., London, were donated to the church. This almost certainly refers to those currently in situ). A gallery was present by 1782. The church was restored in 1813, when the arcades and chancel arch were rebuilt. The church was re-floored, re-seated and re-roofed in 1868, and the octagonal oolite font is also thought to date to this time. The north transept was also restored and the gallery was removed. The church was again restored in 1899. The coalhouse is thought to have been added in the early twentieth century. The stalls are modern.

Sources include:
Cambria Archaeology, 2000, Carmarthenshire Churches, gazetteer, 48
Ordnance Survey, 1887, first edition 25in
Ordnance survey, 1906, second edition 25in

N Vousden, RCAHMW, 26 November 2012