In 1535 Lord Leonard Grey marched to Limerick and Mathew O’Brien surrendered him the Castle of Carrigogunnel on condition it should only be garrisoned by Englishmen. It was said at this time to have been in undisturbed possession of the O’Briens for over two hundred years. The Deputy garrisoned it under the command of George Woodward, “an honest and a hardy man.” In the meantime the fortress was given by indenture to Donough O’Brien to hold for the King. He was son-in-law to the Earl of Ossory, and had long been fawning on the Government with offers to besiege the castle for them, if provided with a hundred men and a piece of ordnance. The governor of the castle, no doubt regarding this arrangement as a violation of the conditions on which the castle had been obtained, handed it back to its former owner, Mathew O’Brien, which the State Papers describe as losing it “by treachery.” This was in 1536, and the same year Lord Butler appeared before it to regain it for his relative, Donough O’Brien. It was garrisoned partly by followers of Desmond and partly by those of Mathew O’Brien. A messenger was sent to them offering them their lives, but otherwise no quarter. They returned no answer, but imprisoned the bearer. A breach was soon made with a battering piece, and after several attempts, the castle was carried by storm. The besiegers lost thirty killed and wounded, while seventeen of the defenders were killed in the attack, and forty-six were afterwards put to death. A few of the principal O’Briens were conveyed to Limerick, tried for high treason, and executed. Large ransoms were offered for these men but were refused. The fortress was then committed to Lord Butler, and he transferred it to Donough O’Brien, who, it is stated, “became a scourge to the citizens of Limerick.” James of Desmond besieged Carrigogunnel in 1538, and the following year great complaints were lodged about the plundering of the neighbouring country by the castle garrison. Towards the close of the year these charges became so serious that Donough O’Brien was deprived of his possession. The castle was in the hands of Brien Duff O’Brien, chieftain of Pobblebrien, in 1590, and is described as being very strong and “a most dangerous place if the enemy were seized thereof.” Donough O’Brien is mentioned as of Carrigogunnel in 1607, yet Brien Duff O’Brien surrendered his possessions and the castle to the Queen and received a patent for the same. He was knighted, and died in 1615. Daniel O’Brien forfeited the castle and lands for taking part in the rebellion of 1641. Charles II. granted Carrigogunnel and four plowlands to Michael Boyle, Lord Archbishop of Dublin. In Thomas Dineley’s Journal he states that it belonged to His Royal Highness, and was at the time rented by the Primate and Chancellor of Ireland. Archdale says that it at one time belonged to the Knights Templars.