Minster-in-Sheppey was one of the early minsters founded in Kent, being founded in 664 as a nunnery by St Sexburgha. The nunnery was burnt down by the Danes in 855. At some time before the close of the Saxon period the church was rebuilt and refounded as a Benedictine nunnery, and incorporates 7th century fabric. Archbishop Corbeuil refounded it as an Augustinian nunnery in 1123, which was dissolved in 1539.
The Benedictine building consisted of two separate but adjacent churches, the conventual church to the North and the parish church to the South. These now form one building, connected by an arcade of pointed arches. The Saxon church to the North shows clear evidence of very early Saxon work, probably 7th century, in the North chancel and nave. The East end of the chancel dates from 1581 when St Katherine's Chapel to the East was demolished. Both churches were altered in the 13th century. The conventual church has a 15th century West tower and widened but foreshortened chancel. The parish church to the South consists of a nave and chancel with South porch. The latter was built in 1879-81 by Ewan Christian. An inventory of 1536 mentions 4 chapels, one of which, St John's, was in the churchyard.