The church has a nave with a S aisle of c.1190, N aisle of 1867, and a chancel which incorporates some Anglo-Saxon or Early Norman herringbone brickwork. The late-12thc. tower rises over the E end of the S aisle.

Westhampnett village and church are mentioned in the Domesday Survey. The manor was held by William from Earl Roger in 1086 and by 2 free men from Earl Godwine in 1066. It was assessed at 9 hides. Later it was held by the family of Paynel, first occuring in 1269 and 1275.

The S aisle and tower are Transitional in style, with some Norman features (e.g. scalloped capitals) and other Early English features (e.g. capitals with smooth bells and slightly overhanging or waterholding mouldings). The composite pier at Westhampnett has been compared with Boxgrove.