It consists of two chambers, known as the branches of Tynwald: the directly elected House of Keys and the indirectly chosen Legislative Council.

The chambers sit jointly, on Tynwald Day at St John's for largely ceremonial purposes, and usually once a month in the Legislative Buildings in Douglas.

The name Tynwald, like the Icelandic Þingvellir and Norwegian Tingvoll, is derived from the Old Norse word Þingvǫllr meaning the meeting place of the assembly, the field (vǫllr→wald, cf.

The Lieutenant Governor of the Isle of Man presides, unless the monarch as Lord of Mann, or a member of the Royal Family representing them, is present.

On some matters, the Royal Assent to Legislation (Isle of Man) Order 1981 requires the Lieutenant Governor to consult with and follow the advice of the Secretary of State for Justice of the United Kingdom.

The year was picked arbitrarily by officials; there is no evidence indicating that such an assembly was held in 979, or that any such event resembled the modern-day court.

In October 1651, during the English Civil War, the island fell to the Parliamentary forces, who took over the administration of the government.

Tynwald was left with no money to spend, and little power, although it was still able to bring about social change by the repeal in 1771 of restrictive labour legislation.

A Royal Commission was appointed in 1791, but it was not until 1866 that Tynwald finally passed legislation that would see some of its members elected for the first time.

Women have been able to stand for election to the House of Keys since the 1919 introduction of universal adult suffrage based on residency.

The opening statement of the Statute Book was "Divers Ordinances, Statutes, and Customs, presented, reputed, and used for Laws in the Land of Mann, that were ratified, approved, and confirmed, as well by the Honourable Sir John Stanley, Knight, King and Lord of the same Land, and divers others his Predecessors, as by all Barons, Deemsters, Officers, Tenants, Inhabitants, and Commons of the same Land where the Lord's Right is declared in the following Words".

Furthermore, the Commissioners' report noted that prior to the revestment, no "minutes or journals" of the proceedings of the Council or the House of Keys had been kept.

…in respect to government and laws, the Manks appear, in all ages to have been a distinct people, and in some degree an independent, or not annexed to any other kingdom… The people, however, beyond all written record, have clearly within claimed and enjoyed the right and privilege of being governed and regulated by laws of their own making, or consented to by themselves, or by their constitutional representative…To maintain this independence of the Legislature, is held to be the first duty of every Manxman… they dread therefore and must ever dread, the interference in their internal concerns, or even a precedent being made for such interference from any other legislature on earth; even the British…In 2007, the island's system of government was reviewed with plans to transform the Legislative Council into a directly elected chamber[citation needed], likely stemming from debate around the reform of the House of Lords, which was a promise of the Blair Government,[13] and resulted in the passage of the House of Lords Act 1999 and the Constitutional Reform Act 2005.

According to the House of Keys Hansard for 6 December 2023, it was stated that the question of removing the Bishop's vote, and possibly seat, in LegCo and Tynwald has been debated ten times in the recent past.