The monument consists of a massively built L-shaped tower house, within a courtyard of which traces of the walls and earthworks survive. Beyond that main nucleus are traces of further earthworks, which are probably the relics of outer courtyards. Amongst these may be traces of earthen siegeworks constructed in 1523, at which time the English commander considered the castle to be the third strongest in Scotland. Cessford Castle was again burned by the English in 1543 and 1544.
The tower is likely to have been built after Andrew Ker of Altonburn was granted a charter of Cessford in 1446. It is massively constructed of red sandstone rubble with ashlar dressings, and there are extensive traces of lime render in more sheltered locations. Its final form may have been partly a result of changes made in the course of construction, and there appear to have been later changes, made perhaps after the siege of 1523. Most unusually, there are two entrances. One is into the basement of the main block, with a dog-legged corridor leading off to one side into the jamb and the spiral stair within the wall thickness at the junction of the two parts. The second entrance is into the flank of the jamb at first-floor level, but the passage within the entrance is of dog-legged plan, giving access to the kitchen in the jamb, the hall in the main block and the stair between the two.
At some uncertain date, the re-entrant angle between the main block and jamb of the tower house were partly infilled by a forework of less substantial construction, and there are traces of another structure attached to the west side of the main block. The main block rose through three principal storeys with garrets above, while the jamb rose through four storeys below the garrets. Although the details are not entirely certain, in its final form the wall-head of the main block appears to have had a covered walk, while the wall-head of the jamb, which was evidently raised to a higher level, had a corbelled-out wall-walk.
The most extensive traces of the courtyard walls and the buildings it contained lie to the north and north-east of the tower house, with evidence of what may have been a gatehouse directly to the north.
The area currently scheduled is limited to the tower house and the main courtyard immediately around it. In order to afford protection to the area likely to have been occupied by the outer courtyards and the earth work vawmures and other works associated with the siege of 1523, the scheduling is to be extended to the whole of the field in which the castle stands. The area to be scheduled is irregular on plan, with maximum dimensions of c.125m from north to south and 239m from east to west.