Before modern democracy, the Isle of Man was ruled by a Governor or Lieutenant Governor, the personal representative of the Lord of Mann, assisted by a Council made up of the permanent officials of the island: the Bishop, the Archdeacon, the Deemsters (the judges), the Attorney General. That council eventually evolved into the Legislative Council, the upper chamber of Tynwald. The whole arrangement changed in 1765 with the Act of Revestment, which transferred the Lordship of Mann from the Duke of Atholl to the British Crown. The trigger was prosaic: smugglers were using the island as a tax-free entrepot for goods bound for Britain and Ireland, and London bought the Lordship to shut the trade down. For the next century the Lieutenant Governor and his officials worked for the British Government, not for the Manx people.

The House of Keys was popularly elected for the first time in 1866, but the elected chamber spent the next half century arguing with Lieutenant Governors who controlled the island's budget and could appoint members of its boards. Conflict came to a head between 1902 and 1918, during the tenure of the 3rd Baron Raglan as Lieutenant Governor. After the First World War, a slow handover began. Commissions in 1911, 1959, and 1969 recommended that real authority move from the Governor to Tynwald. An Executive Council was established in 1949 and gradually became the effective government of the island. Finance and the police came under local control between 1958 and 1976. The Lieutenant Governor stopped chairing the Executive Council in 1980, replaced by a chairman elected by Tynwald. In 1985, the council was reconstituted to include the chairmen of the eight principal Boards, and in 1986 those chairmen were given the title 'Minister.' The chairman became 'Chief Minister.' In 1990 the body was renamed the Council of Ministers.

The 19th-century Boards of Tynwald did the practical work of government in piecemeal fashion. The Board of Education was created in 1872, the Highway Board in 1874, the Asylums Board in 1888, the Government Property Trustees in 1891, the Local Government Board in 1894. Tynwald levied direct taxes, but a Board's freedom to act was constrained by what the Lieutenant Governor allowed in the budget. By the 1950s the structure was unwieldy: dozens of Boards, Statutory Boards, and Commercial Boards overlapping each other. The reform of the 1980s consolidated them into a ministerial government, and a second reorganisation in 2010 produced the modern eight-department structure: Cabinet Office, Education Sport and Culture, Enterprise, Environment Food and Agriculture, Health and Social Care, Home Affairs, Infrastructure, and the Treasury.

Around those departments sit a constellation of statutory boards and other public bodies: the Financial Services Authority (Lught-Reill Shirveishyn Argidoil Ellan Vannin), the Gambling Supervision Commission, the Office of Fair Trading (Oik Dellal Cair Ellan Vannin), the Isle of Man Post Office (Oik Postagh Ellan Vannin), Manx Care (Kiarail Vannin), the Manx Utilities Authority (Bun Shirveishyn Vannin). Every department has both an English name and a Manx Gaelic one. The Treasury is Yn Tashtee. Infrastructure is Rheynn Bun-troggalys. The bilingualism is partly ceremonial, partly a deliberate revival project; only a few hundred people speak Manx fluently, but the language still organises the way the state introduces itself.

On 31 March 2019, the public sector on the Isle of Man employed 7,413 full-time equivalent people across civil service, teachers, nurses, and police. That was about a tenth of the island's population and 21 per cent of its working population. The Civil Service alone had more than 2,000 employees. Defence is not part of the picture; it is the constitutional responsibility of the United Kingdom. Most government offices and Tynwald itself are concentrated in Douglas, the capital, in the Legislative Buildings near the harbour. Government House, the Lieutenant Governor's residence, is a few miles up the coast at Onchan. The Chief Minister works from the Cabinet Office in Douglas. The arrangement is small enough that most Manx residents have met someone in it, and old enough that someone in it has probably attended a Tynwald Day ceremony in the open air at St John's, where laws are read aloud in both languages on a hill that has heard them for a thousand years.