• Australia has a high commission in Nukuʻalofa.^[68]
• Tonga has a high commission in Canberra.^[69]

• Brazil is accredited to Tonga from its embassy in Wellington, New Zealand.
• Tonga does not have an accreditation to Brazil.

• Canada is accredited to Tonga from its High Commission in Wellington, New Zealand.^[70]
• Tonga is accredited to Canada from its Permanent Mission to the United Nations in New York City.^[71]

The Kingdom of Tonga and the People's Republic of China (PRC) established official diplomatic relations in 1998. The two countries maintain cordial diplomatic, economic and military relations.

• China has an embassy in Nukuʻalofa.
• Tonga has an embassy in Beijing.

These neighbouring countries in the South Pacific have a history of bilateral relations going back several centuries.

Fiji's Prime Minister Voreqe Bainimarama received "cheers and thunderous applause" from the Tongan public when he attended a Pacific Islands Forum meeting in Tonga in October 2007; the crowd's "enthusiastic reception" of Fiji's leader was likened to "that accorded to a rock star".^[72] Radio Australia noted that he had been "the star of this year's meeting, for the people of Tonga",^[73] while TVNZ reported that he had been "given a hero's welcome".^[74]

In terms of inter-governmental relations, Tonga has generally avoided pressuring Fiji's "interim government" into holding democratic elections. However, Tongan Prime Minister Dr. Feleti Sevele has urged Bainimarama "to produce a credible roadmap to the election according to the Constitution and law of Fiji".^[75]

• Germany is accredited to Tonga from its embassy in Wellington, New Zealand and maintains an honorary consulate in Nukuʻalofa.^[76]
• Tonga is accredited to Germany from its high commission in London, United Kingdom.

• Diplomatic relations were established in 1984.^[77]
• Greece is accredited to Tonga from its embassy in Wellington, New Zealand.^[77]
• Tonga does not have an accreditation to Greece.

• India is accredited to Tonga from its high commission in Suva, Fiji.
• Tonga does not have an accreditation to India.

• Japan has an embassy in Nukuʻalofa.
• Tonga has an embassy in Tokyo.^[78]

• Tonga and Latvia established diplomatic relations in 2020. On 28 October 2020, Tongan and Latvian Ambassadors to the United Nations signed a joint communiqué formalising the bilateral relations and expressed satisfaction over strengthening of ties between the two countries.^[79]
• Both countries see opportunities for cooperation in tackling climate change, development cooperation, economics, and cooperation in various multilateral formats, especially in the light of the prospective Latvian non-permanent membership of the United Nations Security Council in 2026–2027.^[80]

• Mexico is accredited to Tonga from its embassy in Wellington, New Zealand.^[81]
• Tonga is accredited to Mexico from its Permanent Mission to the United Nations in New York City.^[82]

• New Zealand has a high commission in Nukuʻalofa.^[83]
• Tonga has a consulate-general in Auckland.^[84]

The Kingdom of Tonga and the Soviet Union established formal diplomatic relations in 1976. Tonga was the first Pacific Island country to establish relations with the USSR. The USSR was dissolved in 1991 and was succeeded by Russia as the successor state.

On 2 October 2005, Minister of Foreign Affairs of the Russian Federation Sergey Lavrov and Minister of Foreign Affairs of the Kingdom of Tonga ST T. Tupou exchanged telegrams offering congratulations on the occasion of 30th anniversary of establishing diplomatic relations between the two nations. In his heads of foreign ministries of Russia and Tonga expressed confidence in further development of Russian-Tongan relations in the interests of the peoples of both countries and strengthen peace and security in the Asia-Pacific region.^[85]

• Russia is accredited to Tonga from its embassy in Canberra, Australia.
• Tonga does not have an accreditation to Russia.

Both nations are Pacific Islands countries and members of the Commonwealth of Nations and Pacific Islands Forum.

• Samoa is accredited to Tonga from its Ministry of Foreign Affairs in Apia.
• Tonga is accredited to Samoa from its Ministry of Foreign Affairs in Nukuʻalofa.

The Kingdom of Tonga and the Republic of Korea have established diplomatic relations on September 11, 1970.

• The two countries have good diplomatic relations.
• The ROK's Investment in Tonga in 2019 was about 2.5 million $.^[86]

• Spain is accredited to Tonga from its embassy in Wellington, New Zealand.
• Tonga does not have an accreditation to Spain

• Turkish ambassador in Wellington to New Zealand is also accredited to Tonga.^[87]
• Trade volume between the two countries was negligible in 2019.^[87]

Tonga has had its longest formal relations with the United Kingdom, with which it remains on very good terms. The British explorer James Cook led expeditions to Tonga in 1773, 1774 and 1777. This was followed by extensive English missionary activity beginning in 1797. The mass conversion of most Tongans to Christianity – and primarily to Wesleyan Methodism – resulted in strong religious ties to England as the source of most of the missionaries involved. Indeed, it was in part through the assistance of the English missionary Shirley Baker (who baptized him) that George Tupou I established the current Tonga constitutional monarchy in 1875. This served to further strengthen Anglo-Tongan ties, and the United Kingdom and the Kingdom of Tonga established formal mutual diplomatic recognition in 1879.^[88] While always remaining independent, Tonga became a British protected state under the so-called Treaty of Friendship on 18 May 1900, when European settlers and rival Tongan chiefs tried to oust the second king. The Treaty of Friendship and protected state status ended only in 1970 under arrangements established during the reign of Tonga's third monarch, Queen Sālote.

Tonga is unique among Pacific island nations in its never having been colonized. Its foreign relations, therefore, have always been as an independent monarchy free of the colonial relationships of its neighbors. (see History of Tonga).

Tonga's earliest foreign relations were rooted in conquest of many of its neighboring islands so that by the 12th century, Tongans, and the Tongan kings, the Tu'i Tonga, were known across the Pacific, from Niue, Samoa to Tikopia they ruled these nations for over 400 years, leading some historians to refer to a "Tongan Empire," although it was more so a network of interacting navigators, chiefs and adventurers. Tonga's dominance of the region was greatly affected following first contact with the Dutch beginning in 1616 on the Northern Tongan islands "Cocos Island" (Tafahi) and "Traitors Island" (Niuatoputapu), and later in 1643 on the main island of Tonga itself. The Dutch did not establish a lasting presence, but Dutch reports led to interest from the British. The British explorer James Cook led expeditions to Tonga in 1773, 1774 and 1777. This was followed by extensive English missionary activity beginning in 1797. The mass conversion of most Tongans to Christianity – and primarily to Wesleyan Methodism – resulted in strong religious ties to England as the source of most of the missionaries involved. Indeed, it was in part through the assistance of the English missionary Shirley Baker (who baptized him) that George Tupou I established the current Tonga constitutional monarchy in 1875. This served to further strengthen Anglo-Tongan ties. While always remaining independent, Tonga became a British protected state under the so-called Treaty of Friendship on 18 May 1900, when European settlers and rival Tongan chiefs tried to oust the second king. This protected the Tongan monarchy from European or other colonizing powers in return for a special relationship with the United Kingdom.

In the 1950s, Anglo-Tongan relations were strengthened with the visit of each country's monarch to the other nation. In 1953, Tonga's Queen Sālote became the first Tongan monarch to visit Britain when she attended the coronation of Elizabeth II. Soon after, in 1954, the Queen Elizabeth then visited Tonga.

The Treaty of Friendship and protected state status ended only in 1970 under arrangements established during the reign of Tonga's third monarch, Queen Sālote.

As part of cost-cutting measures across the British Foreign Service, the British Government closed the British High Commission in Nukuʻalofa in March 2006, transferring representation of British interests in Tonga to the UK High Commissioner in Fiji. The last resident British High Commissioner was Paul Nessling.^[89]

In 2010, Tongan Brigadier General Tau'aika 'Uta'atu, Commander of the Tonga Defence Services, signed an agreement in London committing a minimum of 200 Tongan troops to cooperate with Britain's International Security Assistance Force (ISAF) in Afghanistan.^[90]

• Tonga has a high commission in London.
• United Kingdom has a high commission in Nukuʻalofa.

The United States and Tonga enjoy close cooperation on a range of international issues. Officers of the American Embassy in Suva, Fiji, are concurrently accredited to Tonga and make periodic visits since the United States has no permanent consular or diplomatic offices in Tonga. Although plans for a US consulate in Tonga were announced in 2008,^[91][92] it has yet to be established.^[93] In May 2023, the United States announced plans to establish an embassy in Tonga, as part of a larger regional push to strengthen ties with the Pacific.^[94]

Peace Corps Volunteers teach and provide technical assistance to Tongans. A large number of Tongans reside in the United States, particularly in Utah, California and Hawaii.^[95]

• Tonga is accredited to the United States from its permanent mission to the United Nations in New York City and has a consulate-general in Burlingame, California.^[96]
• United States has an embassy in Nuku’alofa.