St Giles's is a large church with a freestanding tower to the SE. The church has a six-bay aisled nave with late 12thc. or early 13thc. arcades and later N and S doorways, the N under a porch. The present, Perpendicular, clerestory is higher than the original, which can still be seen on the outside as a series of round or slightly pointed arches. The chancel was destroyed in a gale in 1741, although the early 13thc. chancel arch survives. It was rebuilt shorter the following year and finally taken down in the 1868 restoration. This was undertaken by the Rector, Canon John Scott, under the direction of his brother, Sir George Gilbert Scott. Construction is of roughly coursed stones with brick repairs. The freestanding tower, begun in the 13thc., is of three storeys, the lowest of stone rubble, the second rendered for most of its height, and the remainder of brick. The ground floor was originally open on all four sides. The nave arcades and chancel arch are described here, although all probably date from the early years of the 13thc.

The manor of Tydd St Giles with the advowson of the church were held by Ely Abbey and then by the bishops after 1109.

Pevsner dates the S arcade a little later than the N on account of the presence of stiff-leaf capitals, but the use of both the beaked and simple chamfered impost profiles on both arcades (and the chancel arch) implies that they belong together. Pevsner and Bradley call them late-Norman or Transitional; the List Description puts them in the late-12thc., while the VCH prefers a 13thc. dating. They are included here because of their scallop capitals, which we consider to be a Romanesque form. The extra decorative emphasis given to the chancel arch is more likely to have liturgical significance than to indicate a later date. Signs of an earlier church survive in the blocked E windows of the nave.