The church has chancel, nave with N and S aisles and N porch, and W tower with a vestry attached on the S. The church was rebuilt by William Butterfield in 1870-72. Some parts of the older stucture were retained. The S aisle is 14thc., the first two stages of the tower are 12thc. and the uppermost stage 14thc. The round-headed tower arch has a chamfered impost, but is otherwise plain. A round-headed window, deeply splayed, survives on the S face of the lowest stage of the tower and now opens onto the vestry. On the exterior the second stage windows of S, E and W faces (the E window is covered by the chancel roof and the W is partially hidden behind the church clock) have a continuous thick roll with inverted cushion bases (partially restored). The church walling is coursed rubble. There is some herringbone masonry visible in the tower walling. Romanesque sculpture is found on a reset fragment in the N aisle. The fragment is not from the church.
A priest at Barley is mentioned in DS as being among the tenants of Harduin de Scales, who held land there. VCH records that the advowson appeared to be in the gift of the tenants. In 1268 it was given to Chatteris Abbey, Cambridgeshire.
The fragment is carved with two foliage scrolls clasped at the centre by a reeded band with a central row of nailhead. The stems are also reeded with nailhead above the level of the clasp. Both scrolls terminate in acanthus leaves, the L contains a ribbed berry and the R a cross-hatched berry. Further leaves wrap around the scrolling stems at the angles. Behind the clasp is a vertical strap with reeding and nailhead which has short tri-lobed leaf terminals at top and bottom. Beneath the scrolls in the centre is a short upward facing tri-lobed leaf. The fine, grey stone is probably Totternhoe Stone, a local limestone.