The church contains a late Norman font and the chancel with its two windows are from the thirteenth century.
Much of the remainder of the building has been restored over the centuries but it still retains much of its Norman character.
The church has the largest roost of Greater Horseshoe Bats in Cornwall and is protected as being a Site Special Scientific Interest (SSSI). Greater Horseshoe Bats are listed in the British and European Red Data Books as they are rare and threatened.
The Church of St. Merteriana is a Historic England Grade I listed building (No.1327702). It was listed on 17 December 1962.