The church has a chancel with S chapel, nave with N and S aisles, S porch and a W tower. The original late 11thc. - early 12thc. church had chancel, nave and W tower. The N aisle is of mid-12thc. date, the S aisle is 14thc. and the clerestory is 15thc. The chancel was rebuilt in the early 14thc. The S chancel chapel and porch are mid-15thc. There are traces of the original plain, round tower arch above the 13thc. opening to the W tower and 12thc. sculpture is found on the arcades.

The church was dedicated by Herbert Losinga, Bishop of Norwich (1094-1119).

The manor of Redbourn, which presumably included the advowson, was given to St Albans Abbey in the reign of Edward the Confessor. Archbishop Lanfranc held the manor for some time, but it was restored to St Albans in the time of Abbot Paul (1077-93). Both Henry II and John I confirmed the grant to St Albans, which held the manor until the Dissolution.

VCH suggests that the N aisle is of c.1140.

Thurlby comments on the similarity between the proportions and mouldings of the S arcade and those at Hemel Hempstead.