This is a long stone and brick church of the fenland consisting of a 14thc./15thc. brick tower and clerestory; an early 13thc. five-bay nave arcade; and an early 14thc. chancel. Chancel renovated in 1869. There are several examples of reused Romanesque sculpture in the chancel and in the nave.

In listing the land of Ivo Tallboys, the Domesday Survey notes a church in Tydd (St Mary) under his lordship in 1086. The church is built on the site of a salt-hill, a remnant of the local salt-making industry in the fenland economy, which drove the construction of large churches in this region (Sawyer).

It is likely that label stops IV.5.c.i, ii, and vi in the chancel are reused corbels given their size; IV.5.c.iii, is clearly a reused 12thc. voussoir; III.3.d.i appears to be good medieval material and in situ. Label stops IV.5.c.iv, v and III.3.d.ii are hard to analyze as their forms are so abstract. Are these medieval? Their rudimentary features and block-like quality are not dissimilar to the rare pair of Anglo-Saxon label stops, which survive at St. Peter, Barton-Upon-Humber (Everson and Stocker). On the other hand, label stops IV.5.c.viii and ix, with their excessive plasticity, are stylistically out of place with the other label stops in the chancel; these look to be later insertions and are very likely part of the 19thc. restoration . Finally, what are we to make of IV.5.c.vii, the running quadruped which seems to mirror III.3.d.i? Is this another product of the 19thc. restoration based on III.3.d.i? Except for III.3.d.i, whose proportion and alignment of the legs with the label argue for this being in situ, all these label stops were probably inserted into their present location during the 1869 renovation of the chancel. The plan of the necking of the re-set volute capital in the S aisle of the nave, IV.5.c.xi, argues for a keeled shaft below it. The nave arcades are c.1200 with the round columns, polygonal capitals (some with partially carved upright leaves), and chamfered two-steps arches which can't quite decide whether to be round or pointed.