In the 12th century, the church was rebuilt and extended by Richard de Clare, then lord of the Manor of Hadlow.

From the Norman Conquest until the 18th century, Hadlow did not have a resident Lord of the Manor, being held under Tonbridge Castle.

Thomas Walter, Yeoman bequeathed 20s in 1448 "To make a window on the north side of the church by the altar of Our Lady".

[7] The church remained under the ownership of the Knights Hospitallers until 1540, when the order was dissolved by Henry VIII.

[9] St Mary's is mostly constructed from ragstone, with some ashlar detail and quoins of Tunbridge Wells sandstone.

The stained glass windows date from the 19th and 20th centuries,[9] the most recent of which is "The Visitation" created by Francis Skeat in 1956.

[10] In 1919, the Coverdale Chair was presented to St Mary's by T E Foster MacGeagh of Hadlow Castle.

The chair is so-named because it was owned by Miles Coverdale, Bishop of Exeter, who made the first translation of the Bible into English.

[7] The fourth, fifth, sixth and seventh are inscribed "Iames Bartlett Me Fecit 1695",[12] and the tenor is inscribed "Henry Barton Edmond Norman Ch Wardens Andrew Reany Vicar 1695 Iames Bartlett Me Fecit".

[7] The organ at the church was presented as a gift by Ernest Hargreaves (who married the then vicar's daughter) and was built by Alfred Monk of Camden in 1880.

Prior to the restoration, it was suggested that the instrument should be replaced by an electric or electronic organ; this advice was not followed.

Other memorials were to Sir Ralph Colcoff, vicar (d. 1514) and Dame Elizabeth Gossand, wife of Henry Fane.

There is a memorial to Sir John Rivers, former Lord Mayor and Sheriff of London, who was a lay rector at St Mary's,[15] and his wife Joan.

[16] In the churchyard, there is a memorial in the shape of an oast house to 30 hop-pickers who were killed in the Hartlake disaster, an accident that occurred while a wagon, taking around 40 hop-pickers and their families back to their camp site, was crossing the flood-swollen River Medway at the poorly maintained Hartlake Bridge on 20 October 1853.