The well-known Anglo-Saxon W tower, which is profusely decorated with raised flat bands (lesenes), may originally have formed the nave of the church. The present nave is essentially Norman, but has added aisles with late-13thc. or early-14thc. arcades and Dec. windows. The chancel is also Norman, but was lengthened in the 13thc. Romanesque features described here are the blind arcading and sedilia within the chancel, with their associated stringcourses and some re-set chevron voussoirs or jamb-stones; the south nave doorway and the tower and chancel arches.

Earl's Barton was held by Countess Judith in 1086, when it was called Bartone or Burtone. No church was recorded at that time. Judith married Waltheof, son of Siward, Earl of Northumbria who in 1065 became Earl of Northampton, and by 1261 the manor had picked up its prefix.

A study of the Norman sculpture of Earls Barton reveals a tradition of preservation and reuse throughout the 13thc. and 14thc., demonstrating that the 12thc. decoration of the church was highly valued in the later medieval period. Formally, the earliest Norman sculptures in the church are the plain cushion capitals of the chancel arch, which was probably built in the early 12thc. as part of a campaign comprising a single nave and chancel. Unusually, a programme of sculptural enrichment in the third quarter of the 12thc. does not seem to have been accompanied by significant construction work. That programme produced the chancel blind arcading and the S doorway. There are sufficient parallels between the two ensembles to demonstrate that they are the work of the same sculptors. The doorway must have been carefully re-set in the late-13thc., when the S aisle was added to the Norman nave. The idea of a single Norman nave with opposing N and S doorways receives some support from the vertical 'jambs' of chevron now illogically situated in the N and S walls of the chancel: these may come from a N doorway which was dismantled when the 14thc. N aisle was added. The awkward fifth and sixth bays of the blind arcades may have been assembled slightly earlier, when the chancel was extended in the 13thc. Their stones, and those forming the stepped sedilia, may have come from a continuation of the arcade along the E wall of the chancel. Finally, when the W tower arch was given a pointed shape in the 13thc., the masons reused Norman voussoirs to form the outer order and label. Taking into account patterns of reuse throughout the rest of the building, it seems likely that these stones originally came from the W tower arch, and date from the mid 12thc. The beakhead on the S doorway is accomplished and very distinctive. Elsewhere in the county, the beakhead ornament is also found at Pitsford and Roade but all three appear to be by different workshops.