Borthwick Castle, Scottish Borders was a 16th-century L-plan tower house, about 1 mile (1.6 km) north west of Duns, Scottish Borders, Scotland.
[1] It is thought that it was a watchtower and small residence, rather than a place of strength.
[2] Borthwick Castle had a courtyard surrounding the 16th-century buildings and a later house.
There was a corbelled-out stair-tower in the re-entrant angle of the L-plan tower.
Apart from narrow brick in the fireplace and window openings the building was constructed from mortared stone.