St Mary’s church is situated on the N side of the historic core of Carisbrooke village near the centre of the island. This consisted mainly of a two-row settlement along a significant EW route-way associated with a gap in the island’s lateral chalk ridge. The church consists of a nave, a S aisle in two parts, a S porch and a W tower. The chancel was demolished c. 1565 (Lloyd and Pevsner 2006, 112-3). The S wall of the nave contains two single-splayed windows which were cut away with the insertion of the late 12th-c arcade of five bays. The part of the aisle corresponding to the two W bays of the arcade is much narrower than the E part, with the former probably representing the width of the late 12thc aisle. The wider part would appear to be a rebuilding of the early to mid-13thc. The porch dates from the 16thc. The tower is dated 1471 on a renewed stone (Lloyd and Pevsner 2006, 113). The priory buildings were situated immediately to the N of the church as indicated by two arched recesses in the external N wall of the nave and the weathering for the former cloister above, with Priory Farm to the N of the churchyard wall.

The Romanesque features are the S arcade, the smaller of the two recesses in the N wall of the nave, the nave N doorway and the incised slab set into the floor at the E end of the nave. The heads and jambs of the two single-splayed windows in the nave S wall are Romanesque but are devoid of any ornamentation.

Domesday Book records that the monks of Lyre held a church in the manor of 'Bovecome' (Munby 1982, 52b). Whilst it has been pointed out that this church may have been located in the vicinity of Bowcombe Farm (Page 1912, 232, 234; Edwards 1999, 3-4), 'ecclesiam sancte Marie de Caresbroc' was included in a confirmation charter of Baldwin de Redvers, between 1142 and 1147, of properties which had been granted to Lyre Abbey by William FitzOsbern (Hockey 1981, 2). Although Carisbrooke church is not explicitly referred to until 1114 (Hase 1988, 61), the church of Bowcombe mentioned in the Domesday Survey can be identified with Carisbrooke church (Margham 1993, 2-3; Margham 2008, 50-1). It is therefore very likely that Carisbrooke was one of the churches given by William FitzOsbern to Lyre between 1067 and 1071. The configuration of parish boundaries and documented relationships between churches indicate that Carisbrooke was a superior church with an extensive parochia. A priory of Lyre was established at Carisbrooke c. 1147 as the centre of the Norman abbey’s interests on the Isle of Wight (Lloyd and Pevsner 2006, 112). The connection with Lyre ceased in 1415 with the grant of the possessions of Carisbrooke priory by Henry V to help endow his foundation of the charterhouse of Sheen (Hockey 1982, 45).

The incised slab depicting a cleric holding a crozier presumably dates from after the foundation of Carisbrooke Priory c. 1147. Lloyd and Pevsner date the earlier recess in the N wall of the nave to c. 1200 and describe it as having 'a rib-moulded rounded arch and short shafts with delicate foliate capitals' (Lloyd and Pevsner 2006, 113).

The nave S arcade, its N doorway and the smaller recess in the N wall all appear to be contemporary. The S-facing side of the N wall of the churchyard incorporates a slab of Quarr limestone depicting a R hand in low relief; the hand is 0.29 m in length. This would appear to be a manus dei (hand of God) dating from the later Anglo-Saxon period but there is a possibility that it may dated to the post-Conquest period.