The site had been fortified in the prehistoric period, but the construction of the castle was undertaken following the division of the Duchy of Normandy in 1204.
The castle was the primary defence of the Island until the development of gunpowder which then rendered the castle ultimately indefensible from Mont Saint Nicholas, the adjacent hill which overlooks the castle. The construction of Elizabeth Castle off Saint Helier was commenced at the end of 16th century to replace Mont Orgueil. Walter Raleigh, Governor of Jersey in 1600, rejected a plan to demolish the old castle in order to recycle the stone for the new fortifications with the words: "'twere pity to cast it down".
The old castle continued to be used as the Island's only prison until the construction of a prison in St. Helier at the end of the 17th century. The Crown found it expedient to send troublesome agitators such as William Prynne and John Lilburne to Mont Orgueil far from the realm of England. The regicides Thomas Wayte, Henry Smith, James Temple, Hardress Waller and Gilbert Millington were transferred to Mont Orgueil in 1661.
A report for the States of Jersey in 1691 declared that the barracks accommodation was so dilapidated that it was impossible to quarter troops there. Two years later, the castle was stated to be in a ruinous condition and subsequently was abandoned as a prison. This was because Elizabeth Castle had been built and the castle was neglected and not needed anymore.
Repairs were carried out 1730-1734 and for the rest of century parts of the castle were adapted for garrison accommodation. In 1800 the Corbelled Tower was fitted out for use by Admiral Philippe d'Auvergne as his headquarters for the secret service organisation he was running in Brittany and mainland Normandy.
In 1846 the castle was visited by Queen Victoria and Prince Albert. The castle has also hosted subsequent royal ceremonies to welcome George V in 1921 and Elizabeth II; inscriptions mark the occasions.
Until the second half of the 19th century the castle was open to the public on one day a year, Easter Monday, and crowds used to flock from all over the Island. This is believed to be a survival of the pre-Reformation custom of visiting St. George's Chapel inside the castle on St. George's Day.
Left in a generally ruinous state by the British government at the time of its handover to the people of Jersey by the Crown on June 28 1907, Mont Orgueil has been managed as a museum site since 1929, although during the Second World War German Occupation (1940-1945) the occupying forces garrisoned the castle and added modern fortifications camouflaged to blend in with existing structures.
The heritage site has been managed by the Jersey Heritage Trust since 1994. Aspects of the Trust's plans have been the subject of controversy between historians, politicians and the public - in particular plans to build a Tudor hall inside the castle keep.
In 2004, a commemorative Jersey pound note was put into circulation depicting Mont Orgueil.
On 2 April 2006, after a long building programme the castle was reopened to the public by the Lieutenant-Governor of Jersey. Restoration work has opened up previously inaccessible areas of the castle to the public. Newly built additions in modern style have enclosed sections of the castle and made them weatherproof, parts of the structure have been reinterpreted, and artistic interventions in the grounds and structure of the castle have provided attractions for visitors.