The church, one of the largest in the Vale of Glamorgan, stands in the small village of Penmark. It consists of a nave and separate chancel, embattled west tower and south porch. Inside, the transitional chancel arch is pointed with chevron ornament on its west side. There is a rood stair in the north wall of the nave. The original south-west window in the nave is Decorated with two trefoil-headed lights surmounted by a quatrefoil. The south door has been dated to the fourteenth century and the west tower was added in the fifteenth or sixteenth century with a monumental Perpendicular arch opening into the nave (Orrin (1988), 301, 303; Newman (1995), 504). Restorations, during which most of the windows were replaced or renewed in the Perpendicular style, took place in 1800, around 1860 and in 1893 (Clark and Jones (1861), 6; Orrin (1988), 297, 299, 304). The font is probably thirteenth century. There are two loose pieces of chevron-carved stone in the churchyard.

The earliest historical evidence for the church at Penmark dates from the thirteenth century. In 1254, the church was assessed at £20 in the ‘Valuation of Norwich’ (Lunt (1926), 315). In the assessment of ecclesiastical incomes in England and Wales ordered by Pope Nicholas IV in 1291, Penmark was valued at £16 and recorded as impropriated to the abbey of Gloucester (Denton and Taylor (1998), 137, 147). Gloucester’s possession of Penmark has been questioned, seemingly in favour of Tewkesbury (Green (1906–7), 63; Rees (1950), 143). However, in the accounts of the receiver of the abbot of Tewkesbury for parts of Glamorgan for 1449–50, the church of Penmark is referred to as ‘lately appropriated to the monastery of Tewkesbury’ (Rees (1950), 180).

Penmark Castle stands around 40m north of the church. Although not mentioned in documentary sources until 1307, the castle was probably founded by the Umfraville family in the early twelfth century (Royal Commission (2000), 280).

The close association between the castle and the church, prompted Thurlby to observe: ‘While no Romanesque stonework remains [at the castle], the juxtaposition of church and castle is an excellent example of this sort of Norman pairing of ecclesiastical and secular’. If the church did originate in the early twelfth-century, no evidence survives from that date. The oldest feature in the church is the transitional chancel arch, which Thurlby suggests is not earlier than the end of the twelfth century (Thurlby (2006), 179).

The pronounced step on the south side of the chancel arch and the height of the entrance to the rood stair in the north wall of the nave (1.02m) may suggest that the nave floor was lowered at some point. Orrin notes that during the 1893 restoration, both nave and chancel were refloored and the sanctuary floor was raised (Orrin (1988), 299, 304).

The use of lateral chevron decoration and a cogwheel edge on the voussoirs of the chancel arch and the two loose chevron-carved stones found in the churchyard may point to a similar date for both. The loose pieces may have come from the original south door or the north door. The north door, which would have provided access from the nearby castle, has been blocked, but its position is marked by a pointed relieving arch.