The oldest parts of the church, in the nave and some doorways, date from the 12th century. The chancel was added in the 14th century and the whole church re-roofed at the end of the 16th century.
Major restorations took place from 1855 onwards, including most of the windows, which account for its mostly Victorian feeling inside
When visiting the church, before entering, the first item of interest to note is a small sundial, on which is the date 1581.
On entering the porch, which was a 15th century addition to the church, one can see the ancient and beautifully carved doorposts or jams, which are on either side of the main door. They are probably Norman although they support an arch of a later date.
Once inside, the nave is the oldest part of the church. In earlier times, there would have been no seating for the congregation. The church pews were added in the 19th century.
In the ceiling above, most of the wood used is modern, but the date 1599 appears on one of the trusses. The corbels, or stone supports, are carved in the form of four heads and may date from the 15th century.
There is a large victorian stained glass window (1892), near to the pulpit. It depicts Jesus in the garden of Gethsemane.
The chancel dates from between 1325 and 1350 and stands on an earlier Norman site. There is a medieval piscena in the south wall. In the north wall there is a small blocked door, probably originally used by the priest. The choir stalls are victorian. The Communion Table was made in the early 17th century and was renovated in 1968.
On the north wall of the nave, beside the organ, is a memorial to Alexander Burrell, his wife and daughter, and beside the list of rectors is a monument to Thomas Egerton, erected in 1720. There are also pictures of some of the rectors of Adstock in the bottom of the tower.
In the late 15th century, when the upper walls of the nave were erected, the tower was built. The west wall of the tower has stained glass windows which were added in the 19th century, they depict St. Peter and St. Paul, and are a memorial to John Hart, rector who died 1n 1867
The font dates from about 1490, is octagonal and made from stone, and lined with lead. The lead has carved in it, "graffiti", some of the lettering is in a gothic style. The font cover is modern.
Within the belfry, which is on the floor of the tower above the church clock, hangs three bells, two large bells and a Sanctus bell. The oaken bell frame dates from 1618 and carries the inscription "JOHNIELTS". Treble bell dates from the 15th century and was made by John Sturdy, it bears the inscription "SANCTA ANNA ORA PRO NOBIS". The tenor bell was made by Richard Chandler at Drayton Parslow, and bears the inscription "RICHARD CHANDLER MADE ME 1676". The Sanctus bell dates from 1826 and has the name Thomas Mears. This is the only bell which is rung now.
Details of the stained glass in the church can be found on the following web sites (the site includes many photos):
Wesleyan Methodist worship was held in Adstock in a converted barn from 1834, until a chapel was constructed here in 1889.