The church has a nave, a S porch, a wide S aisle which ends in a chapel, and chancel. The aisle chapel and SW tower were builtc.1200, and the chancel dates from the 13thc.

Ashurst is not mentioned in the Domesday Survey. The church was restored in 1720 and 1877, when the S porch was rebuilt. The font was found embedded in an internal buttress. Although it may be 12thc. in origin, the carved arcade is Gothic, and probably dates from 13thc. The arcade is notionally formed, however, from intersecting round-headed arches. The similar font at Buxted is carved with pointed arches enclosing trefoil tracery.

The font is dated to the 13thc. by Steer.