Duart Castle was probably built by Clan MacDougall in the 13th century, and appears to have come into the hands of Clan MacLean in the following century.
In 1350 Lachlan Lubanach Maclean of Duart, the 5th Clan Chief, married Mary, daughter of John of Islay, Lord of the Isles and Duart was part of her dowry.
In 1647, Duart Castle was attacked and laid siege to by the Argyll government troops of Clan Campbell, but they were defeated and driven off by the Royalist troops of Clan MacLean.
In September 1653, a Cromwellian task force of six ships anchored off the castle, but the Macleans had already fled to Tiree. A storm blew up on the 13 September and three ships were lost, including HMS Swan.
In 1678, Archibald Campbell, 9th Earl of Argyll, son of the Marquess of Argyll, successfully invaded the Clan MacLean lands on the Isle of Mull and Sir John Maclean, 4th Baronet fled the castle and withdrew to Cairnbulg Castle, and afterward to Kintail under the protection of the Earl of Seaforth.
In 1691 Duart Castle was surrendered by Sir John Maclean, 4th Baronet to Archibald Campbell, 1st Duke of Argyll. The Campbell clan demolished the castle, and the stones from the walls were scattered. Donald Maclean, 5th Laird of Torloisk used some of the stones to build a cottage for his family close to the site of the castle.
By 1751 the remains of the castle were abandoned.
Descendants of Archibald Campbell, 1st Duke of Argyll sold the castle in 1801, to MacQuarrie, who then sold it to Carter-Campbell of Possil who kept it as a ruin within the grounds of his own estate to the north, Torosay Castle. He later sold his Torosay Estate which now included the ruins of Castle Duart to A. C. Guthrie in 1865. On 11 September 1911, the ruin was separated from the rest of the Torosay Estate and was bought by Sir Fitzroy Donald Maclean, the 26th Chief of the Clan MacLean and restored.
In 2012, the centenary of the 1912 restoration, the Chief of Clan Maclean announced that his family could no longer afford the upkeep of the castle in light of the expense of major repairs. In the winter of 2013-14 the castle lost four ceilings, which were brought down by water penetration through the chimneys. In July 2014, a Restoration Appeal was launched.
The castle was used as a location in the 1999 film Entrapment, starring Sean Connery (who has MacLean ancestry on his mother's side) and Catherine Zeta-Jones. The castle also features prominently in the 1971 film When Eight Bells Toll, starring Anthony Hopkins.
It is also the setting for the base of Buffy Summers in the first half of Buffy the Vampire Slayer Season Eight.