St Saeran's Church, Llanynys, is a large double-nave type parish church. The thirteenth century northern chamber is of earlier date than the southern, but both chambers have been extended and perpendicular style roofs added around 1500. A porch was added in the sixteenth century, and it was substantially restored around 1768. Further minor alterations were made in the nineteenth century. It is constructed of limestone rubble with red sandstone blocks at the western end, and has a slate roof. There is a seventeenth century bellcote on the southern chamber. There are ten bay roofs to both chambers, with alternating arched-braced collar and hammerbeam trusses.

There are notable wallpaintings including a probable fifteenth century depiction of St Christopher on the north wall at the western end of the northern aisle. It is a large painting with the Christ-child, hermit, chapel and windmill also included. The saint has a tall rough staff with leaves and he wades through a river with very lively and identifiable fish (possibly including a lamprey). The background is diapered with IHS monograms. Above St Christopher is a Welsh inscription with a border in black-letter text from Haggai 1.4.8. It is probably sixteenth or seventeenth century in date. On the south wall of the south aisle is a Royal Arms on canvas in oils, dated 1661. It is a very fine composition with elaborate "leafy" initials CR (cf Gwydir-uchaf Chapel).

Source: Richard Suggett, Painted Temples: Wallpaintings and Rood-screens in Welsh Churches, 1200–1800, (RCAHMW 2021), pp. 14, 130–1, 235, 261.

RCAHMW 2022