The church is of coursed flint construction with Kentish ragstone quoins, plinths and other detailing. The tooling of some of this ragstone, particularly the porch quoins, is indicative of it having been reused from an earlier Saxon chapel. In 1883 St Mary’s was completely restored and the small vestry constructed on the south side of the chancel.
The church has a mixture of Decorated and Perpendicular windows, which are post medieval in date and were presumably installed during the church’s 1883 restoration: fragments of the originals are preserved in the churchyard wall. The only surviving original windows are a single quatrefoil light in the west wall of the aisle and a series of small rectangular openings in the tower’s upper stages.
The church retains original openings to the porch and between the porch and the aisle, each of which is pointed and of several simple orders. Other surviving medieval furniture is the door to the tower spiral staircase, a stoop in the porch, a trefoil piscine in the south wall of the chancel and a simple octagonal font which has been relocated outside the church and now stands by the porch.
The two lead glazed ceramic memorial plaques reset into the south elevation in the vicinity of the extension doorway are rare examples of their type. They are the work of the Wrotham Potters, who were active between 1612 and 1739. They record the deaths of two children of Edward Woodden, constable to the Hundred of Wrotham who served in that capacity with Jacob Heath in the year 1636.
The oldest tombstones in the churchyard date from 1715. One gravestone belongs to the author and composer William Edward Hickson (1803-1870) whose words feature in the English national anthem. Sir Sydney Waterlow was buried in Stansted churchyard in 1906. He was a commissioner at the Crystal Palace Exhibition and was director of the Union Bank of London. In 1872 Sir Sydney became Lord Mayor of London.