Adjoining the ramparts in the south-east of the town stands the Parish Ghurch, as it has now become since the union of the three Sandwich parishes in 1948; this was formerly the election place of the Mayors of Sandwich. There are many carved headstones in an ancient and extensive churchyard. The central tower and east and west part of the nave belong to a twelfthcentury aisleless church, in the thirteenth century the chancel was rebuilt with a north chapel and in the fourteenth century a south chapel was added.
Originally the Church was cruciform in plan, as was characteristic of Norman buildings, but the addition of chantries and chapels produced the present shape and dimensions. The Norman tower is one of the finest in England and the pillars which support it have rounded arches and curiously carved capitals with various ornamentations of scrolls, frets, foliage and grotesque figures.
In the north-west angle of these columns is the doorway to the spiral tower-staircase over which is an interesting tympanum with late Saxon or early Norman carvings. The octagonal heraldic font has on one of its faces the arms of ancient Sandwich, and on the south face the Arms of Archdeacon Robert Hallum by whom it is believed the font was given about I406. Over the north door is the 'Priest's Room', and other interesting features are the oak stalls of the members of the Confraternity of St Clement, one of which is a miserere seat; and many indents of brasses, one of which was of the Bishop of Ross, Vicar of this parish in 1444. The High Altar Cross, Processional Cross and the chalice and paten in daily use are the work of the great silversmith Omar Ramsden.

The fine organ with remote console was dedicated by the Bishop of Croydon in I951. St Margaret's Chapel has a complete medieval tiled floor, also a Gradas (gospel step) built into the altar dais; two altar stones each marked are now restored to their proper use after having been used as tombstones. There is a fine Hagioscope between this Chapel and the High Altar. The Chapel of St George has been restored and the ornaments were dedicated by the Bishop of Dover in 1953. The bronze statue of the Madonna and Child is the work and gift of a local sculptor, Mr. L. H. R. Byng. The Chapel also contains a statue of St John which was taken from Lincoln Cathedral by the Puritans. The Mayor's scal which faces this Chapel bears the date 1869.