Constitutional safeguards include freedom of speech, press, worship, movement, and association. The judiciary is independent of the executive and the legislature.

The Head of the Commonwealth, or simply Queen of Papua New Guinea, is represented in Papua New Guinea by a governor general who acts on the advice of the prime minister and the cabinet. The Governor-General of Papua New Guinea is elected by parliament.

The governments of Papua New Guinea are characterized by weak political parties and highly unstable parliamentary coalitions. The prime minister, elected by Parliament, chooses the other members of the cabinet. Each ministry is headed by a cabinet member, who is assisted by a permanent secretary, a career public servant, who directs the staff of the ministry. The cabinet consists members, including the Prime Minister and ministers of executive departments. They answer politically to parliament.

The Governor General appoints the Chief Justice of the Supreme Court on the advice of the Prime Minister and the Leader of the Opposition. The Governor General appoints the other justices with the advice of a judicial commission. The Judicial Committee of the Privy Council (based in the United Kingdom) serves as the highest appellate court.

Papua New Guinea has a unicameral National Parliament, previously known as the House of Assembly. It has 109 seats, with 89 elected from single-member "Open" electorates and 20 from province-level "Provincial" electorates. Members are elected by popular vote to serve five-year terms. The most recent election was held in June–July 2012.

Members of Parliament are elected from the nineteen provinces and the National Capital District. After independence in 1975, members were elected by the first past the post system, with winners frequently gaining less than 15% of the vote. Electoral reforms in 2001 introduced the Limited Preferential Vote system (LPV), a modified version of alternative vote, where voters number their first three choices among the candidates. The first general election to use LPV was held in 2007.

Parliament introduced reforms in June 1995 to change the provincial government system, with Provincial members of Parliament becoming provincial governors, while retaining their national seats in Parliament. However, if a provincial member accepts a position as a cabinet minister, the role of governor falls to one of the Open members of Parliament from the province.

Papua New Guinea's judiciary is independent of the government. It protects constitutional rights and interprets the laws. There are several levels, culminating in the Supreme Court of Papua New Guinea.

There is a Supreme Court of Papua New Guinea, not separately constituted but an appellate Full Court of the National Court. Its Chief Justice, also the Chief Justice of the National Court, is appointed by the Governor General on the proposal of the National Executive Council after consultation with the Minister responsible for justice. Other justices of the National Court, who are available to sit as members of ad hoc benches of the Supreme Court, are appointed by the Judicial and Legal Services Commission.