The tower is an independent structure attached to the west end upon piers, with archways at the north and south ends to give access to the south entrance to the church and churchyard. The tower is 131 feet high and is the most striking feature in this part of the Stour Valley. John Constable, the great Suffolk painter, has included it in many of his pictures, notably Dedham Mill (in the Victoria and Albert Museum, London), The Vale of Dedham (in the National Gallery of Scotland), and A View of the Stour (in the Huntingdon Art Gallery, Pasadena, California, USA).

The archway under the tower is very unusual and has been given the name of the "Galilee" porch. It is enriched with Tudor heraldic symbols such as the Beaufort portcullis and the Tudor Rose, and among them may be seen not only the Webbes' initials and trade mark, but also on small rosettes two portrait heads in burgess costume. These are, it is thought, to be of John Webbe and his wife Joan. They can be seen in the top row of the eastern side just above the second portcullis, counting from the north.

The tower was added to the church and finished in 1519. There was no room for a procession to pass round the outside of the church without encroachment upon vicarage property and for this reason the archway through the tower was constructed. In order to make the Galilee porch as wide as possible, the lower stairway up to the ringing chamber had to be placed inside the west door of the church on the south side.