St Mary's has an aisled and clerestoreyed nave, the arcades of five bays and now on very tall piers; octagonal on the N side and cylindrical on the S. The piers and the pointed arches date from well into the 13thc., but most of the capitals are reused 12thc. pieces. The remodelling of the arcade is contemporary with the aisle windows, which are also slightly earlier on the S. Both nave doorways are 13thc. and set under 13thc. vaulted porches, but the S is larger and more elaborately carved. The chancel has a Perpendicular S chapel, now used for the organ. The W tower is of three storeys with a broach spire, and largely belongs to the second half of the13thc. Construction is of coursed stone rubble, with ashlar for the top storey of the tower, the spire and the S chapel. The church was restored by Sir George Gilbert Scott in 1875-76. 12thc. sculpture is found in the nave arcade capitals and possibly also in reset corbels high on the interior aisle walls.

According to the Anglo-Saxon Chronicle, King Edgar gave Warmington to Peterborough Abbey in 963. It was still in the abbey's hands in 1086, mostly held directly but with one hide held by two knights and a further hide and a half by Isembard and Rozelin. No church was recorded until 1146, in a bull of Eugenius III confirming Peterborough's possessions, but RCHME VI suggests that it might well have existed earlier, since the benefice was comparatively wealthy. The church provided a pension for the sacrist of Peterborough, which was increased from 20s to two marks by Abbot William de Waterville (1155-75).

Dedication to St Mary recorded in 1521.

Benefice of Warmington and Tansor and Cotterstock and Fotheringhay and Swick.

The simple geometrical decoration is similar on all seven corbels, but the upper projections of those in the S aisle are an unusual elaboration. S aisle corbel 4 best shows that they must originally have clasped a wall plate rather than simply acting as brackets. Waterleaf capitals similar to those in the arcades are found at nearby Duddington.