The church has a chancel with attached vestry, nave with N aisle and S porch, and W tower. The nave is 12thc., the N aisle late 13thc. and the W tower and chancel 15thc. (The lower part of the tower is late 14thc. and the top stage is 19thc.) The chancel was remodelled in the 17thc. The porch is late 16thc. or early 17thc. A restored doorway in the S wall of the nave may be partially 12thc., and 12thc. material survives in the S wall and NE and NW angles of the nave. The exterior is rendered apart from the N wall which is flint with brick buttresses, and the top stage of the tower which is flint and ashlar.

The Domesday Survey does not mention a church at Datchworth. In 1086 the Domesday Survey records that the Abbots of Westminster Abbey had the overlordship of Datchworth. One hide was held by Ansketel from Lanfranc, Archbishop of Canterbury. Three hides and one virgate were held directly by Westminster Abbey. VCH records that three further virgates of land in Datchworth were held by two knights, of Geoffrey de Bech (2 ½ hides), and by Robert, of Peter de Valognes (½ hide). Hugh de Bocland held the manor, which included the advowson, in 1192. (VCH, 81)

Pevsner reports that the church was originally enclosed by a moat, but doesn’t mention the doorway (137).

VCH states that the doorway is modern (80), as does the RCHME (85), but the Transactions of the East Herts Archaeological Society (69) state that it is original, albeit with modern pillars of Mansfield marble. The author records that the doorway was left in situ during the 1875 restorations and 'carefully restored' by a Mr Lawrence, presumably the architect responsible for the 1875 work. Cussans also notes that the doorway is the only surviving 12thc. architectural feature (198). The whitewash covering the doorway obscures details, but some features, such as the capitals and bases, may be 12thc.