The original structure, some of which may date from the 14th century, has four storeys. A further two storeys were added above the parapet in 1626, with Renaissance windows bearing the initials SIDKH (Sir John and Dame Katherine Hamilton). The entrance to the Tower had a lean-to hoarding from which items could be dropped, for instance boulders, hot sand, or boiling oil. Preston Tower was purchased by the National Trust for Scotland in 1969. It is currently under the guardianship of East Lothian Council.