The church's walls are built of mixed rubble, septaria, flint, pebbles and freestone, with dressings of limestone.

The earliest components of the church all date to the 14th century. The chancel, north nave arcade and north aisle are dated to c.1330-40, and at the same time or shortly afterwards the north vestry was added. The west tower is basically late 14th-century and in the 15th century the church was embellished - the south arcade, aisle and porch were built or rebuilt and the chancel arch was rebuilt. About 1500 the north and south chapels were built or rebuilt and the clearstory was added. The rood stair was rebuilt in c.1530. The church was damaged in the siege of 1648 and repaired afterwards (the church was outside the siegeworks encircling the town). It was repaired and beautified again in 1724. The top of the tower was rebuilt in brick in c.1820 and the church was restored and reseated by W.A. Moy of London in 1865. Damage was done by the earthquake of 22 April 1884 and there was restoration afterwards by W. Scargill, when the top of the tower was again rebuilt. Further work was carried out in 1898.<1> The church has a good early C16 hammer beam roof to the nave.<2><3><4><8>

The earliest record for a church on this site is c.1150 when Maurice de Haie gave the church of 'Hethe' to St John's Abbey who still held the advowson in 1257.<5>

In 1290 there was an Anchorites cell here occupied by Agnes.<7>

Presumably, the foundation of St Leonard's must be directly linked to the development of the early medieval port at the Hythe and the settlement that grew up around it. In 1997, however, an Anglo-Saxon buckle was found nearby, raising the question of whether the Hythe port and St Leonard's date back as far as the Saxon period.<6>

Three digital photographs of St Leonard's Church, taken August 2016.<9>