As the Republic of China did not recognize Mongolia until 1945, both countries did not exchange any diplomats between 1946 and 1949, and Mongolia recognized the People's Republic of China in 1949. There have never been formal diplomatic relations between Mongolia and Taiwan.
Outer Mongolia declared independence from the Qing Dynasty in 1911, the same year in which the Republic of China was established following the Xinhai Revolution. Under the terms of the 1946 Sino-Soviet Treaty of Friendship, the Republic of China recognised Mongolian independence. However, due to a border conflict on the Khovd/Xinjiang border, no diplomatic relations were established in the 1946-49 period. In 1952, three years after the ROC's retreat to Taiwan, the ROC government accused the Soviets of violating the treaty; the following year, the ROC's Legislative Yuan voted to abrogate the treaty.
Taiwan continued to occupy China's seat in the United Nations until 1971 and used its position as a permanent member of the UN Security Council to block the admission of the Mongolian People's Republic into the UN throughout the 1950s. The only veto cast by the ROC during its membership in the UN was in 1955, against the admission of Mongolia. Thus, Mongolia was excluded from the UN until 1960, when the Soviet Union announced that unless Mongolia was admitted, it would block the admission of all of the newly independent African states. Faced with this pressure, the ROC relented under protest.
The Legislative Yuan of Taiwan applied for a constitutional interpretation on 12 April 1993 to ask what the boundaries of the ROC national territory would be, while considering Outer Mongolia not included in the ROC territory. However, the Judicial Yuan of Taiwan, in its Interpretation 328 on 26 November 1993, called the constitutional territory beyond the reach of judicial review and thus avoided the question as whether Mongolia should be considered the constitutional territory of the Republic of China.
Ninety-one years after Mongolia's first declaration of independence, Taiwan did not recognise Mongolia as an independent country; official maps of the Republic of China showed Mongolia as Chinese territory. Relations began to improve in 2002, when the Executive Yuan under a Democratic Progressive Party administration announced that Mongolian nationals would be entitled to visas rather than entry permits when travelling to Taiwan, the same as individuals from foreign countries; however, the Kuomintang-controlled Legislative Yuan criticised the implementation of the decision, as they had not been consulted. Later, representatives of the two governments agreed to open offices in each other's capitals; Taipei's office in Ulan Bator was opened in September of that year. Taiwan's Ministry of the Interior then decided to discontinue including Mongolia on its official maps of Chinese territory, and on 3 October 2002, the Ministry of Foreign Affairs announced that Taiwan recognizes Mongolia as an independent country. In 2002, the Taiwanese government excluded Mongolia from the definition of the "mainland area" for administrative purposes. In 2006, old laws regulating the formation of banners and monasteries in Outer Mongolia were repealed. However, the official borders of the Republic of China have not been changed to exclude Outer Mongolia via a vote of the National Assembly (as required by the Constitution prior to 2005) or via a referendum (as required by the Constitution after amendments made in 2005). The official status of recognition is currently ambiguous, though in practice Mongolia is treated as an ordinary foreign power.
Citizens of Taiwan may travel to Mongolia using Taiwan passports (as is the case for most countries except the PRC), but Mongolian visas are stapled into (and not applied directly) onto the passport and Mongolian immigration authorities stamp the stapled visa instead of the passport. This is also the case for Hong Kong visas and entry/exit stamps.
- "Onward to Mongolia", Taiwan Review, 2003-01-01, retrieved 2010-01-04
- Liu, Weiling (1997-08-15), "Mongolian visitors draw attention to border debate"[dead link], Taiwan Journal, retrieved 2010-01-04
- "Taipei Sources Hint Veto on Outer Mongolia", Washington Post, 1955-11-20, retrieved 2008-02-05
- "Taiwan Veto Likely; Taipei Regime May Again Bar Outer Mongolia From U.N.", The New York Times, 1961-04-22, retrieved 2008-02-05
- Legislative Yuan Constitutional Interpretation Application (in traditional Chinese), Judicial Yuan, 1993-04-12, retrieved 2008-12-22
- Judicial Yuan Interpretation 328 translated by Professor J. P. Fa, Judicial Yuan, 1993-11-26, retrieved 2008-12-22
- "Major Taipei decision alters Mongolia's status", China Post, 2002-02-27, retrieved 2008-02-05
- "Mongolian office to ride into Taipei by end of the year", Taipei Times, 2002-10-11, retrieved 2008-02-05
- Yearbook of the Republic of China (中華民國年鑑): The land of the Mainland Area (in traditional Chinese), Government Information Office of the Republic of China (Taiwan), 2005, retrieved 2008-12-22