The church consists of chancel with S chapel, nave with N and S aisles, S porch and clerestorey, and W tower. The earliest surviving features are the two-bay 12thc. N and S arcades (the S extended later in the middle ages into the chancel to allow better access to the S chapel). A plain 12thc. blocked, round-headed window survives in the W wall of the N aisle. The clerestory is early 15thc. and the tower c.1200. The upper part of the tower and possibly the outer walls of the aisles were rebuilt in the 15thc. The 14thc. chancel was rebuilt in the early 15thc. and substantially restored after a fire in 1969. The S chapel is 14thc. and the S porch is 18thc. 12thc. sculpture is found on the capitals and arches of the N and S arcades. The church is constructed of flint rubble and Totternhoe stone.
VCH records that Abbots Langley was given to St Albans Abbey by Aethelwine the Swart and his wife Wynfleda in the reign of Edward the Confessor.
The Domesday Survey does not mention a church, but states that the manor was held by the Abbot of St Albans. One hide was appropriated by Herbert son of Ivo 'in the time of the Bishop of Bayeux' and was held by the Count of Mortain in 1086. The Domesday Survey also records that there was a priest at Abbots Langley.
The advowson remained in the Abbey's hands until the Dissolution.
Of two bays, with round-headed arches. Shallow water-holding bases, usually on square, stepped, chamfered plinths, support round piers and half-round responds. There is no E respond to the S arcade. All capitals have necking and the impost is chamfered with a groove along the upright. There are two orders in the arch. The first order has angle roll on inner and outer angles, the second order is plain on the outer angle, but the inner has a fine double-step then a roll followed by a row of chevron carved frontal to the face of the arch. The label has a row of round billet.
E respond: The stepped plinth has angle roll around the step. The capital is multi-scallop above necking (with eight scallops on the W face and four on N and S faces) with volutes on each angle over a thick, vertical row of pellet. There are beaded wedges between the cones, although the central wedge on the E face has no beading. The S volute is grooved, the N is damaged. The shields have a row of beading along their lower edge.
E face: Circular shields. From L to R: The SE volute has a vertical row of pellet below a pointed strap which extends onto the body of the volute. Shields 1 and 2 have shallow recessed centres and lozenge-shaped beading, 3 and 4 have deep recessed centres with fine beading and 5–8 have inverted jelly-moulds. The NE volute has a vertical row of drilled holes along its body.
N face: Semicircular shields, each containing a six–petalled half–daisy. Shields 4–8 have a pellet marking the centre of the flower. The NW volute is damaged.
S face: As shields 3–4 on E face apart from 7 and 8 which are as 1 and 2 on E face. The cones below shields 5 and 6 have a fine vertical line at the centre.
W respond: The base is mostly cut away. The capital is multi-scallop (with eight scallops on the E face and 4 on N and S faces) with fluted and beaded volutes. Beaded, pointed mouldings lie between the cones, although the central pointed moulding on the E face is plain. A groove outlines the shields.