The nave and chancel are Norman. The apse is well preserved, with three windows. Pentlow church is one of six round towered churches in Essex. The main construction of the church is flint and pebble rubble with dressings of limestone and clunch. The tower (which has walls four feet thick) and north chapel date from the 14th century, although the north chapel was rebuilt in the 17th century. Inside the church a Norman west doorway survives: it would originally have been the main doorway into the church but today leads into the round tower.