Carlingford Castle's west wing was built in the late 12th century by Hugh de Lacy, Lord of Meath shortly after the Norman invasion of Ireland.

It acquired the name "King John's Castle" after King John, Lord of Ireland, supposedly stayed there for three days in 1210, during his second expedition, when he invaded Ulster to apprehend Hugh de Lacy, 1st Earl of Ulster.

Local myth claims that he began to draft Magna Carta (agreed in 1215) at Carlingford.

[citation needed] During the Irish Confederate Wars, the castle was held by the Irish Catholic Confederation; then was taken by Sir Henry Tichborne, 3rd Baronet (Parliamentarian) in 1642, then by Murrough O'Brien, 1st Earl of Inchiquin in 1649 and Charles Coote, 1st Earl of Mountrath in 1650.

[6] The curtain wall in the west wing had a gate house and a square flanking tower.