St Celer's Church was a medieval parish church known as 'Merthyr Celer'. Historic and modern Ordnance Survey mapping depicts a possible large outer curvilinear enclosure, but this is not visible west of the A484. The old vicarage is located some 280m north of the church, adjacent to the boundary of the possible enclosure. The vicarage was appropriated to a Cistercian abbey, and was later a posession of the Bishops of Saint Davids. The rectory was in patronage of the Crown until the early nineteenth century, at which time it was appropriated by St David's College, Lampeter. Tithes were subject to a long-standing division between the 'Gwlad' and the 'Grange'. In 1833 these were divided between the Principal and tutors of Lampeter, the vicar and the Llysnewydd family. In the late seventeenth or early eighteenth century Lhyud noted that, according to local tradition, Saint Geler's sepulture was located near the door of the south chapel. Lhuyd also noted a spring with well chapel, known as Ffynnon Geler(NPRN 418071), located not far from the church at the bottom of a steep hill. Ffynnon Geler was renowned for its healing properties, and was said to be visited by 'such a concourse of people that no fair in Wales can equal it in multitude'. It was reportedly visited by the infirm in summer and particularly from 21st June to St Peter's day (29th June). After bathing people are said to have lain down on the 'Llech' located in the churchyard, and if they could sleep they were certain to be cured. At that time, local people reportedly remembered seeing the crutches of 'some infirm persons' left behind in the church 'in memory of their having been cured by bathing in this well'.

The earlier church was whitewashed and consisted of a chancel, nave and south chapel. The chapel occupied the full length of the chancel and the eastern two bays of the nave, which it was divided from by an arcade of pointed arches. In 1850 there was a square-headed three-light window in the chapel's east wall, and sash windows in the church's north walls. There was a shallow niche over the nave west door, with double bellcote above.

The current church is a grade II lited building, constucted of slate rubblestone. It was erected in 1858 on the footprint of the medieval church, to the design of Charles J. Davies. It consists of two-bayed chancel, five-bayed nave, west porch and two-bayed north vestry. All openings are neo-gothic. The exterior is butressed. In 1928 a hot water heating system was installed.

Sources include:
Cambria Archaeology, 2000, Carmarthenshire Churches, gazetteer, 48
Jones, F, 1992, The Holy Wells of Wales, pg 164

N Vousden, RCAHMW, 5 December 2012