The Cook Islands maintains diplomatic relations with various countries and is a member of multilateral organisations. While the country is in free association with New Zealand, which can act on the Cook Islands' "delegated authority [...] to assist the Cooks Islands" in foreign affairs, the Cook Islands nevertheless enters into treaty obligations and otherwise "interacts with the international community as a sovereign and independent state."

In the 1980s the Cook Islands became a member of several United Nations specialized agencies: the World Health Organization in 1984, the Food and Agriculture Organization and UNESCO in 1985, and the International Civil Aviation Organization in 1986. The Repertory of Practice of United Nations Organs records that in 1988 New Zealand declared "that its future participation in international agreements would no longer extend to the Cook Islands..." In 1991 the Cook Islands became a full member of the United Nations Conference on Environment and Development (UNCED) Preparatory Committee and the Intergovernmental Negotiating Committee for a Framework Convention on Climate Change (INC), which the Repertory of Practice describes as "further evidence that the international community had accepted the Cook Islands as a “State” under international law." The United Nations Secretariat therefore "recognized the full treaty-making capacity of the Cook Islands" in 1992 and the Secretary-General, in his capacity as the depository of multilateral treaties, decided that the Cook Islands could participate in treaties that were open to "all states".

List of countries with which the Cook Islands maintains diplomatic relations:

The following countries have established consular relations with the Cook Islands only.