St Mary's Church, Tal-y-Llyn, is situated within a curvilinear churchyard, whose eastern end is probably a later extension. There are two entrances, both with lych gates, in the north and south-west walls of the churchyard. The south-west lych gate (NPRN 400401) is said to have been so placed in order to ensure the safe passage of parishioners to and from church when there were floods. In the porch is a plaque dated 1837, detailing 'Charities to be distributed among paupers in the parish of Tal-y-llyn'.

The church is a Grade II* listed building, whose fabric is medieval, but it has been so heavily restored that dating has not been possible. It consists of a continuous nave and chancel, with a south porch and south chapel. The church once contained a chantry alter dedicated to the Virgin Mary. The square font is thought to be late Norman in date. The nave and chancel are thought to be original, although a slight difference in alignment along the north wall indicates that the latter may be later. The roof is divided by a mixture of trusses, some of which are thought to be medieval. A small rectangular stone trough, with tapering sides, is also thought to be medieval in date. The timber chancel ceiling is thought to date to the fifteenth century. It is divided into forty eight square panels with a grotesque mask forming a boss in the middle of each. Each panel is subdivided into four smaller panels by painted cabling. Each small panel is painted with either a red rose on white, or a white rose on natural wood (earlier evidence suggests the natural wood was originally green). The canopy over the altar has painted roses and grotesques. The chapel was probably added in the sixteenth century. A gallery and new belle-cotte were built in 1765. The gallery was removed in 1876 when the church was restored and modernised. The building underwent further restoration in 1914, when the east wall was rebuilt. All existing windows date from these phases of restoration. The church is now redundant.

Sources include:
Beverley Smith, J, Beverley Smith, Ll, 2001, History of Merioneth II, 366-7
Gwynedd Archaeological Trust, 2000, Historic churches of Gwynedd: gazetteer, 391
Richard Suggett, Painted Temples: Wallpaintings and Rood-screens in Welsh Churches, 1200–1800, (RCAHMW 2021), pp. 3, 114, 118.

RCAHMW 2022