It was built in the 15th century as a chapel of ease to serve St Ceidio's Church, Rhodogeidio, about 0.75 miles (1.25 km) to the east.

[2][4] There is no physical division between the nave and the chancel, although one account in the 19th century said that there had originally been a screen separating them, and some traces of it still remained at that time.

[2][6] Entrance to the church was through a doorway with a square head, in the north wall at the west end; this dates from the 19th century.

[2][5] The 1937 survey noted a bell dating from 1717 and some portions of 17th-century panelled seating near the pulpit; these were not recorded when the church was given listed status in 1970.

[2] Cadw (the Welsh Government body responsible for the built heritage of Wales and the inclusion of Welsh buildings on the statutory lists) also notes that despite its "very poor condition", St Mary's "is a virtually unaltered late Medieval building (even retaining the original roof trusses) and in its isolation, is characteristic of many churches on the island.