St Clydai's Church is situated within a curvilinear churchyard, very close to the line of a possible Roman road. The site almost certainly dates to the early medieval period. Early medieval `bishop house? site, Llangene Fawr, is situated within the parish, some 3.5km south-east of the church. The church was listed in the 1291 Taxatio. A chapel, Eglwys Trisant (NPRN 422372), formerly stood in the churchyard. It was recorded in c.1700 and probably originated as a capel-y-bedd. Three early medieval carved stones, Clydai 1 (NPRN 422368), Clydai 2 (NPRN 422370) and Clydai 3 (NPRN 421735) are situated within the church building, at the west end of the south aisle. The church was a parish church in the post-Conquest period, belonging to the Deanery of Emlyn. It is thought to have belonged to Whitland Abbey. In 1536 the prebendery of Clydau was the rector, but the advowson belonged to the Bishops of St Davids and gave its name to a prebend stall in the cathedral to which the recorial tithes of the parish were annexed.

The church is a Grade II listed building, constructed of slate rubble. It was described as a `very old and handsome building? 1849, although it was in a bad state of repair at that time. The present church consists of chancel, 4-bayed nave, 4-bayed south aisle, north porch and 2-storeyed west tower. The square, cushioned font bowl is thought to date to the 12th or 13th century, and features mouldings, including figures. The nave may date to the 14th century. In its north wall is a stoup with square, scalloped bowl and 2-centred head of later medieval form. The south aisle, traditionally known as Capel Mair, is thought to date to around 1500. Towards its east end is a plain, square aumbry which is thought to be contemporary. The west tower is thought to be early 16th century in date and has retained most of its original openings. The church was restored in the late 19th century, when a new chancel and the porch were built. The upper half of the rood loft stair was blocked at this time. The north half of the church was extended east by one bay, with the addition of a chancel and 2-centred moulded chancel arch. The arcade between nave and south aisle was rebuilt as four bays of arches on cylindrical piers. The church (except for the tower) was entirely refenestrated and the chancel, nave and south aisle were given new, softwwod roofs. The north door was rebuilt and the north porch added.

Sources include:
Dyfed Archaeological Trust, 2000, Historic Churches Project, Pembrokeshire gazetteer
Dyfed Archaeological Trust, 2003, Early Medieval Ecclesiastical Sites Project, Pembrokeshire gazetteer

N Vousden, 21 November 2017