The Domesday Book records that in 1086 Odo, Bishop of Bayeux and King William's half-brother, was the overlord of the manor of Cassington; he designated as mesne lords Wadard of Cogges and Ilbert of Lacy.
The church was founded in 1122 by the elder Geoffrey de Clinton, Chamberlain to King Henry I, who held one of the manors in Cassington and built it as a chapel attached to his residence; it was dedicated to St Peter and consecrated by 1123. Sir Geoffrey de Clinton laid the church under the jurisdiction of Eynsham Abbey. It was called a chapel as late as 1406, and Eynsham retained the advowson until the Dissolution.
Cassington is now part of a joint benefice with Eynsham.