The earliest part of Otterston Castle, built about the end of the 16th century, is the L-shaped central main block lying E-W with the wing projecting from the W end. The barmkin, running N and attached to the E wall of the wing, was probably an afterthought. The entrance is close to the northern of the two surviving towers which stood on the barmkin. Two wings were added within the barmkin in the 17th century. Extensive modern additions and alterations have been made.
D MacGibbon and T Ross 1892; RCAHMS 1933, visited 1925.
Otterston Castle has been demolished except for a 16th century barmkin tower and some adjacent fragments of walling of indeterminate date. The tower, of rubble masonry with stone dressings, is of two storeys with a modern parapet. Two small gun-loops in the second storey face NE and SE respectively.