St Cynllo's Church is situated within a roughly rectilinear churchyard, bounded by the Nant Cynllo (depicted as Pistill-Cynllo on historic Ordnance Survey mapping) on its south side. The churchyard appears to have been extended to the north and is depicted on historic Ordnance Survey mapping as curvilinear. The house names, Gilfach (some 200m north-east) and Cil-bronau (some 350m south-east), may reflect early monastic origins. The church was a parish church during the medieval period, belonging to the Deanery of Sub-Aeron. The rectory was a possession of Talley Abbey. In 1546 Mwnt and Llechryd were free chapels within the parish. In 1833 the living was a rectory in the patronage of the Principal and Tutors of St David's College, Lampeter.

The church is a Grade II* listed building, constructed of slate rubble. It consists of three-bayed nave, three-bayed chancel, south porch and vestry (north of chancel). The square, cushioned font bowl may be medieval in date (retooled in the nineteenth to twentieth century). In 1711 the church was extensively repaired. There was an eastern spire by 1810. The church was rebuilt in 1830-1832, to the designs of David Evans, Cardigan, Fishguard and Eglwyswrw. The extent of the rebuild, and whether any earlier fabric was retained, is not known. The nave and chancel chancel were rebuilt at this time, with a neo-classical spire in dressed and moulded slate rising externally from the chancel arch. the porch may also have been added. The church was again restored in 1860, to the designs of R.J. Withers, London. The vestry was added and the porch was either added or rebuilt. The church was refloored, reseated and replastered, and the present ceilings were inserted. The stalls and pews also date to this time. The spire was rebuilt to its original design in 1993.

Sources include:
Cadw, Listed Buildings Database
Ordnance Survey, 1888, first edition 25in

N Vousden, RCAHMW, 21 November 2013