St Tyfei's Church is situated within an irregularly shaped, curvilinear churchyard, on the southern edge of woodland at Dinefwr Park, Llandeilo. A late first-early second century Roman Fort Complex (NPRN 402271) is set on the ridge above. The churchyrard is bounded by a stream on its north-west side. Foundations noted in levelling the churchyard around 1770 were thought to represent a Roman temple. An altar was recorded, but is now lost. It had carvings of a cornucopia & augural staff on opposite faces. The church site is depicted as the site of a Roman temple on historic (1886) Ordnance Survey mapping. A later Roman coin hoard was found some 230m north-west of the church around 1800, and the findspot (NPRN 419158) is also depicted on historic (1886) Ordnance Survey mapping.

The medieval church was almost entirely rebuilt in 1875. The church's octagonal fifteenth century font is now at St Teilo's Church, Llandeilo (NPRN 100867).

The current church dates from 1875, and may have been built to the designs of R. Kyrke Pearson, Oswestry. It is a Grade II listed building, constructed of rubble stone with freestone dressings. It consists of nave and chancel, south aisle, west porch, north vestry, lean-to south vestry and west double bellcote. The south aisle may retain some medieval fabric, and features a blocked pointed doorway. The three-bay aisle arcade has octagonal piers and hoodmoulds. By the late twentieh century the church was ruinous, and was subsequently leased by the Wildlife Trust, who restored the building for use as an interpretation centre.

Sources include:
Brewer CSIR GB fasc. 5: Wales (1986), 61
Cadw, Listed Buildings Database
Dyfed Archaeological Trust, Historic Environment Record
Ordnance Survey, 1889, first edition 25in

RCAHMW, 8 July 2013