This ancient and lovely 13th Century church follows the traditional Celtic style of nave and chancel with lancet windows. The south aisle was added in the 14th century. The Blounts, the local "Lords of Sodington" added a 16th century North Chapel to provide them with a final resting place. This put Mamble into a small group of parish churches where an Anglican Church had a Roman Catholic chapel. The family moved away and the chapel deteriorated. The remains of the chapel illustrate the change from sandstone to brick.
St Johns Church was built from local yellow sandstone. At the west end of the nave is a plain 13th sandstone font standing on a moulded stem. Many memorial plates are to be found in the church. The Mortimers, Lords Marchers, leave their memory in the form of a cross-legged knight. Other memorial tablets were of the Meyseys of Shakenhurst and the Blounts of Sodington. An older memorial brass is found in the east of the chancel nailed into a stone slab. It consists of an engraved knight and his lady and a dog. The memorial is a tribute to John Blount and his wife, Katherine.
Preserved in the east window is a piece of 14th glass representing the Crucifixion. The colour is in an excellent state of preservation. The background is formed of blue-diapered lozenges divided by bands of red glass. The figure of Christ, although primitive, is very delicate and beautiful.
The 12th century bell tower is the only one of two such wooden towers in England. It is unique in that so much of the original timber remains. The four main supports were made of oak and these supported the wooden bellcote capped by the wooden spire. Later the tower was incorporated in the church by the building of a surround wall of local yellow sandstone. A large programme of restoration has been carried out, to firm up the tower walls and to repair the ancient wooden oak timber frames. The interior of the tower is lit so that visitors can see the timbers which have now been so carefully preserved.