Caisteal Tioram is usually assigned to the 13th -14th century with conspicuous 16th - 17th century remodelling; it is also an Iron Age site with possible Bronze Age antecedents. Symbolic of this early occupancy is the fragmentary bronze hanging-bowl of 4th - 5th century date which is now in the West Highland Museum in Fort William. The earliest parts of the structure visible above ground belong probably to the Norse period - the main topographical features of the area are defined with Norse place-names - and a structure of this nature and proportions suggests a link with the powerful realpolitik and counterculture of Somerled and Clann Somhairle, and to Alexander II's challenge to Norse hegemony; observable facts would suggest an early 13th century date for Caisteal Tioram.
Early charter evidence (coireachain an fhearainn) shows that "Elan Tirrim" was the "headhouse" of the great western Lordship of Garmoran, the power base of the Clann Ruari branch of the Clann Somhairle and the most important part of the northern mainland territories of the Lordship of the Isles. Garmoran also included the Small Isles, South Uist and Benbecula. In later generations Casteal Tioram remained as the mainland stronghold of Clan Ranald and, as such, formed the nucleus of a remarkable kin territory in the Gaelic tradition; the Household or Court of Mac 'ic Ailein was served by families of ecclesiastics, bards and musicians, doctors, lawmen, stewards and metalworkers (eg at High Mingarry), holding office hereditarily in dynasties - an aristocracy of learning. this "cultural landscape" has still to be more fully explored.
By tradition Caisteal Tioram and Borve in Benbecula were built by Amie McRuari, wife of the first Lord of the Isles and mother of the first Clanranald chief, in about 1350. However, a charter of her aunt Christina's from the 1320s, and similarities with Mingary Castle, suggest that the curtain walls at least are somewhat older. Throughout the Clanranald era (ie. 15th - 19th centuries), Tioram was a byword for the patronage and achievements of the Gaidheal and clan Danald - it is reiterated in conventional clan panegyric both in the classical and vernacular traditions. The Castle is also the focus of later oral tradition, especially for the reign of the great John of Moidart, and in the 17th and 18th centuries, drawing on the memories of Iain Ban Sgardois (John MacDonald of Scardoish c.1770-1860), and transmitted by Rev Fr Charles MacDonald, and of "North Argyll".
Reputedly the castle was captured just once, by a party of raiding Campbells, but was quickly recaptured. It survived extensive naval bombardment by government forces in 1554, and possibly also by commonwealth forces in 1658. Allan, the 14th chief, fought at Killiecrankie in 1689 in support of the deposed King James VII, and subsequently for France on the continent. Castle Tioram was confiscated, and garrisoned by government troops from 1693-1715. It was retaken by Allan on his way to fight in the 1715 Jacobite rising, and burnt so as not to fall into government hands when - as he foresaw - he died in the rising.
The ruined castle was eventually given back to Allan's successors, and retained by them even after the 20th chief sold almost all the clan lands in the early 19th century. Owners of the adjacent Loch Shiel estate carried out work on the castle, notably extracting 16th century cannonballs from the southwestern and eastern walls.
The castle was eventually sold in 1905 by the 22nd chief to the owner of Loch Shiel estate, Lord Howard of Glossop. After the latter's death it was sold in 1925 to James Wiseman Macdonald of Los Angeles, under whose ownership the Ministry of Works carried out some works of consolidation; it was his grandchildren who put the castle up for sale in 1997.