The 1960 Constitution, which formally came into force with independence from New Zealand in 1962, is based on the British pattern of parliamentary democracy, modified to take account of Samoan customs. Samoa's first Prime Minister was Fiame Mata'afa Faumuina Mulinu’u II, one of the four highest ranking paramount chiefs in the country. Two other paramount chiefs at the time of independence were appointed joint heads of state for life. Tupua Tamasese Mea'ole, who died in 1963, leaving Malietoa Tanumafili II sole head of state until his death on 11 May 2007, upon which Samoa became, de jure, a republic. The next Head of State Tuiatua Tupua Tamasese Efi was elected by the legislature on 17 June 2007 for a fixed 5 year term.

The unicameral legislature (Fono) consists of 49 members serving 5-year terms. Forty-seven are elected from territorial districts by ethnic Samoans; the other two are chosen by non-Samoans with no chiefly affiliation on separate electoral rolls. Universal suffrage was extended in 1990, but only chiefs (matai) may stand for election to the Samoan seats. There are more than 25,000 matais in the country, about 5% of whom are women. The prime minister is chosen by a majority in the Fono and is appointed by the head of state to form a government. The prime minister's choices for the 12 cabinet positions are appointed by the head of state, subject to the continuing confidence of the Fono. The judicial system is based on English common law and local customs. The Supreme Court of Samoa is the court of highest jurisdiction. Its chief justice is appointed by the head of state upon the recommendation of the prime minister.