The church was not mentioned in the Domesday Book, but Eartham belonged to Aldingbourne manor and was held by the Bishop of Chichester. Between 1157 and 1169, Bishop Hilary gave the church to Richard, the chaplain of Chichester, with two houses, five acres of land and specified tithes, Richard undertaking to have mass said weekly for the bishop's brother, Robert. It was restored in 1869.
The round-headed chancel arch is composed of two orders. The arches are quite plain, and the imposts have a high upright face, with no groove, and a plain chamfer. The inner arch descends onto carved capitals on half-columns; the bases are composed of two superimposed rolls, without a scotia.
The N capital is carved with crooks or stems, which rise to form angle volutes, with the exception of that on the E face, which curls inwards. Between these, on the main face, is an animal head (rabbit?) with long, upright ears. Flanking it are hollow chip-carved triangles and below it is a strange motif with three cusps on the top.
The S capital is also carved with crooks or stems, which rise to form angle volutes. Between these, on the main face, is a bearded male head, flanked by hollow chip-carved triangles.
The outer order descends onto plain jambs, but the upper course of that on the S side has been replaced by a projecting block.