St Cynllo's Church is situated within a curvilinear churchyard, some 700m east of the site of St Mary's Church (NPRN 303779). The church is situated to the immediate south of Llangynllo Farm, which is depicted as Glebe Farm on historic (1888 and 1905) Ordnance Survey mapping. The old Rectory is sited some 60m west of the church. The church was a parish church in the medieval period, belonging to the Deanery of Sub-Aeron. At that time the benefice was in the patronage of the freeholders of the parish. In 1833 the living was a dischaged rectory, still in the patronage of the parish freeholders. A wood, Allt y Ffynnon is situated some 300m west of the church, roughly mid-way between St Cynllo's and the site of St Mary's. The church is parish church to Bronwydd Mansion (NPRN 106563), some 650m to the south-south-west. In 1903 there had been a custom, some 50 years before, of removing brass coffin plates before burial and hanging them up in rows in the church- after a time, they were taken down by relatives, or stored away in the chest.

The church was rebuilt in 1810. It was entirely rebuilt in 1870, to the designs of John Middleton, Cheltenham, on the same foundations as its predecessor. The current church is Grade II* listed as the best example in south-west Wales of a High Victorian estate church, with exceptional polychrome interior and carved work. It is constructed of limestone rubble with oolite dressings and consists of two-bayed chancel, four-bayed nave, two-storeyed south tower with porch, vestry and organ chamber (north of chancel). The vestry was added in 1897. The tower has a disused semi-octagonal spiral stair turret leading to its upper storey.

Sources include:
Cadw, Listed Buildings Database
Cambria Archaeology, 2000, Ceredigion Churches, gazetteer, 48
Eyre-Evans, 1903, Cardiganshire and its Antiquities

N Vousden, RCAHMW, 18 November 2013