St Cwyfan's church is located at the centre of the small village of Tudweiliog, in a large churchyard used as a cemetery. It is a nineteenth-century church on the site of a medieval predecessor. The church was founded by St. Cwyfan, a 7th century saint, the son of Brwynen Hewn; and served as a landmark to mariners sailing to and from Liverpool. It was rebuilt 1849 to designs of George Gilbert Scott (who also designed the fittings) for Charles Wynne of Cefnamlwch. It is constructed of dark rubble masonry with slate roofs. More elaborate than other Llyn churches, it was built in Decorated style throughout and consists of buttressed nave and chancel, west double bellcote projecting over the buttressed west wall, gabled south porch, and gabled north vestry. Stained glass includes works by Clayton & Bell (1906). The churchyard overlies settlement features on the west (NPRN 15189).

(Sources: R.Haslam, J.Orbach & Adam Voelcker, Buildings of Wales: Gwynedd (2009), p.529; RCAHMW air photos: 965031/70 & 965032/41-2; Google Street View, November 2010)
RCAHMW, 26.04.2018