Although born in the U.S., Lattimore was raised in Tianjin, China, where his parents, David and Margaret Lattimore, were teachers of English at a Chinese university. (His brother was the classics translator Richmond Lattimore. One of his sisters was the children's author Eleanor Frances Lattimore.) After being schooled at home by his mother, he left China at the age of twelve and attended schools in Switzerland and England, but returned in 1919 when it turned out that he would not have enough funds for attending university. He worked first for a newspaper and then for a British import/export related business. This gave him the opportunity to travel extensively in China and time to study Chinese with an old-fashioned Confucian scholar. His commercial travels also gave him a feel for the realities of life and the economy. A turning point was negotiating the passage of a trainload of wool through the lines of two battling warlords early in 1925, an experience which led him the next year to follow the caravans across Inner Mongolia to the end of the line in Xinjiang.

The managers of his firm, however, saw no advantage in subsidizing his travels, though they did send him to spend a year in Beijing as government liaison. During the year he spent there before departing on his expedition, he met his wife, Eleanor Holgate. For their honeymoon they planned to travel from Beijing to India, he overland, she by rail across Siberia, a mammoth feat in the first half of the 20th century, but in the event the plans were disrupted and she had to travel alone by horse-drawn sled for four hundred miles in February to find him. She described her journey in Turkestan Reunion (1934), he in The Desert Road to Turkestan (1928) and High Tartary (1930). This trip laid the ground for his lifelong interest in all matters related to the Mongols and other peoples of the Silk Road.

Upon his return to America in 1928, he succeeded in receiving a fellowship from the Social Science Research Council for further travel in Manchuria, then for the academic year 1928/1929 as a student at Harvard University. He returned to China 1930-1933 with fellowships from the Harvard-Yenching Institute and the John Simon Guggenheim Memorial Foundation.

In 1933, he became editor of Pacific Affairs, published by the Institute of Pacific Relations, which he edited from Beijing. Rather than have bland official statements, he made it his policy to make the journal a "forum of controversy." As he later recalled, he was "continually in hot water, especially with the Japan Council, which thought I was too anti-imperialist, and the Soviet Council, which thought that its own anti-imperialist line was the only permissible one...." As explained below, others later accused him of motives which were less scholarly than political. Lattimore sought articles from a wide range of perspectives and made the journal a forum for new ideas, especially from the social sciences and social philosophy. Scholars and writers of all persuasions were contributors, including Pearl S. Buck, some Chinese literary figures, and dedicated Marxists.

After sojourns in New York and London and a trip to the Soviet Union, the Lattimores returned to Beijing in 1937. Owen visited the Communist headquarters at Yan'an to act as translator for T. A. Bisson and Philip Jaffé, who were gathering material for Amerasia as an activist journal of political commentary. There he met Mao Zedong and Zhou Enlai. He was impressed with their candor, but had a less favorable experience on his visit to the party school for national minorities. When he spoke to the Mongols in Mongolian, his Chinese hosts broke off the session.

Following the German invasion of the Soviet Union in June 1941, President Franklin D. Roosevelt appointed Lattimore U.S. advisor to Chinese Nationalist leader Chiang Kai-shek. In 1944, Lattimore was placed in charge of the Pacific area for the Office of War Information. At President Roosevelt's request, he accompanied US Vice-President Henry Wallace on a mission to Siberia and to China and Mongolia in 1944, for the US Office of War Information. The trip had been arranged by Lauchlin Currie, who recommended to FDR that Lattimore accompany Wallace. During this visit, which overlapped the D-Day landings, Wallace and his delegation stayed 25 days in Siberia and were given a tour of the Soviet Union’s Magadan concentration camp at Kolyma. In a travelogue for National Geographic, Lattimore described what little he saw as a combination of the Hudson's Bay Company and the TVA, remarking on how strong and well-fed the inmates were and ascribing to camp commandant Ivan Nikishov 'a trained and sensitive interest in art and music and also a deep sense of civic responsibility'. In a letter written to the New Statesman in 1968, Lattimore justified himself by arguing his role had not been that of 'snoop(ing) on his hosts.

During the 1940s, Lattimore came into increasing conflict with another member of the IPR's board, Alfred Kohlberg, a manufacturer with long experience in the China trade whose visit to China in 1943 convinced him that stories of Chiang Kai-shek's corruption were false. He accused Lattimore of being hostile to Chiang and too sympathetic towards Chinese Communists. In 1944, relations between Kohlberg and Lattimore became so bad that Kohlberg left the I.P.R, and founded a journal Plain Talk intended to rebut the claims made in Pacific Affairs By the late 1940s, Lattimore had become a particular target of Kohlberg and other members of the China Lobby. Kohlberg was later to became an advisor to Senator Joseph McCarthy, and it is possible that McCarthy first learned of Lattimore through Kohlberg.

Meanwhile, accusations were made which later became public. On 14 December 1948, Alexander Barmine, former chargé d'affaires at the Soviet Embassy in Athens, Greece, advised Federal Bureau of Investigation agents that Soviet GRU Director Janis Berzin had informed him prior to Barmine's 1937 defection that Lattimore was a Soviet agent, an allegation Barmine would repeat under oath before the Senate McCarran Committee in 1951.

In March 1950, Joseph McCarthy accused Lattimore of being the top Soviet agent in executive session of the Tydings Committee. The committee, chaired by Senator Millard Tydings, was investigating McCarthy's claims of widespread Soviet infiltration of the State Department. When the accusation was leaked to the press, McCarthy backed off from the charge that Lattimore was a spy, but continued the attack in public session of the committee and in speeches. Lattimore, he said, "in view of his position of tremendous power at the State Department" was the "'architect' of our Far Eastern policy," and asked whether Lattimore's "aims are American aims or whether they coincide with the aims of Soviet Russia." At the time, Lattimore was in Kabul, Afghanistan, on a cultural mission for the United Nations. Lattimore dismissed the charges against him as "moonshine" and hurried back to the United States to testify before the Tydings Committee.

McCarthy, who had no evidence of specific acts of espionage and only weak evidence that Lattimore was a concealed Communist, in April 1950 persuaded Louis F. Budenz, former editor of the Communist Party organ Daily Worker to testify. Budenz had no first hand knowledge of Lattimore’s Communist allegiance and had never previously identified him as a Communist in his extensive FBI interviews. In addition, Budenz had in 1947 told a State Department investigator that he "did not recall any instances" that suggested that Lattimore was a Communist, and had also told his editor at Collier's magazine in 1949 that Lattimore had never "acted as a Communist in any way." Now, however, Budenz testified that Lattimore was a secret Communist, but not a Soviet agent, that is, he was a person of influence who often assisted Soviet foreign policy. Budenz said his Party superiors told him Lattimore's “great value lay in the fact that he could bring the emphasis in support of Soviet policy in non-Soviet language.” The majority report of the Tydings committee cleared Lattimore of all charges against him; the minority report accepted Budenz's charges.

In February 1952, Lattimore was called to testify before the Senate Internal Security Subcommittee (SISS), headed by McCarthy's ally, Senator Pat McCarran. Before Lattimore was called as witness, investigators for the SISS had seized all of the records of the Institute of Pacific Relations (IPR). The twelve days of testimony were marked by shouting matches which pitted McCarran and McCarthy on one side against Lattimore on the other. Lattimore took three days to deliver his opening statement; the delays were caused by frequent interruptions as McCarran challenged Lattimore point by point. McCarran then used the records from the I.P.R. to ask questions that often taxed Lattimore's memory. Budenz again testified, but this time claimed that Lattimore was both a Communist and a Soviet agent. The Subcommittee also summoned scholars. Nicholas Poppe, a Russian émigré and a scholar of Mongolia and Tibet, resisted the committee's invitation to label Lattimore a Communist, but found some of his writings superficial and uncritical. The most damaging testimony came from Karl August Wittfogel, supported by his colleague from the University of Washington, George Taylor. Wittfogel, a former Communist, said that at the time Lattimore edited the journal Pacific Affairs, Lattimore knew of his Communist background; even though they had not exchanged words on the matter, Lattimore had given Wittfogel a 'knowing smile'. Lattimore acknowledged that Wittfogel's thought had been tremendously influential, but said that if there had been a smile, it was a 'non-Communist smile' Wittfogel and Taylor charged that Lattimore had done 'great harm to the free world' in disregarding the need to defeat world Communism as a first priority. They also asserted that the influence of Marxism on Lattimore was shown by his use of the word 'feudal'. Lattimore replied that he did not think that Marxists had a 'patent' on that word.

In 1952, after 17 months of study and hearing, involving 66 witnesses and thousands of documents, the McCarran Committee issued its 226-page, unanimous final report. This report stated that 'Owen Lattimore was, from some time beginning in the 1930s, a conscious articulate instrument of the Soviet conspiracy', and that on 'at least five separate matters', Lattimore had not told the whole truth. One example: 'The evidence... shows conclusively that Lattimore knew Frederick V. Field to be a Communist; that he collaborated with Field after he possessed this knowledge; and that he did not tell the truth before the subcommittee about this association with Field....'

In 1952, Lattimore was indicted for perjury on seven counts. Six of the counts related to various discrepancies between Lattimore's testimony and the IPR records; the seventh accused Lattimore of seeking to deliberately deceive the SISS. Lattimore's defenders, such as his lawyer Abe Fortas, claimed that the discrepancies were caused by McCarran deliberately asking questions about arcane and obscure matters that took place in the 1930s. Within three years, federal judge Luther Youngdahl dismissed the charges. Four of the charges were dismissed as insubstantial and not judicable; denying that he was sympathetic to communism was too vague to be fairly answered; and the other counts were matters of little concern, those which a jury would be unlikely to convict on matters of political judgment. In his book Ordeal by Slander, Lattimore gives his own account of these events up until 1950.

The American Center for Mongolian Studies, together with the International Association of Mongolian Studies and the National University of Mongolia School of Foreign Service organized a conference entitled, "Owen Lattimore: The Past, Present, and Future of Inner Asian Studies" in Ulaanbaatar, Mongolia on August 20 and 21, 2008.

A Leeds student housing block is now named after him. While there, he also promoted the establishment of a Mongolian Studies Department. Lattimore had a lifelong dedication to establishing research centers to further the study of Mongolian history and culture. He is one of the few Westerners to have received recognition from the Mongolian state. The State Museum in Ulaanbaatar named a newly discovered dinosaur after him.

In An Inner Asian Approach to the Historical Geography of China (1947), Lattimore explored the system through which humanity affects the environment and is changed by it, and concluded that civilization is molded by its own impact on the environment. He lists the following pattern:

1. A primitive society pursues some agricultural activities, but is aware that it has many limitations.
2. Growing and evolving, the society begins to change the environment. For example, depleting its game supply and wild crops, it begins to domesticate animals and plants. It deforests land to create room for these activities.
3. The environment changes, offering new opportunities. For example, it becomes grasslands.
4. Society changes in response, and reacts to the new opportunities as a new society. For example, the once-nomads build permanent settlements and shift from a hunter-gatherer mentality to a farming society culture.
5. The reciprocal process continues, offering new variations.

By Owen Lattimore

• 1928: The Desert Road to Turkestan. London: Methuen, 1928. Reprinted:- Boston: Little Brown, 1929; New York: Kodansha International, 1995.

• 1930: High Tartary. Boston: Little Brown, 1930. Reprinted:- New York: Kodansha International, 1994.

• 1932: Manchuria: Cradle of Conflict. New York: Macmillan, 1932; rev. ed. 1935.

• 1934: The Mongols of Manchuria: their tribal divisions, geographical distribution, historical relations with Manchus and Chinese, and present political problems; with maps. New York: John Day, 1934; reprint:- New York: H. Fertig, 1969.

• 1934: "China and the Barbarians," in Joseph Barnes, ed. Empire In The East. New York: Doubleday, 1934; repr. 1970 ISBN 0836918630.

• 1940: Inner Asian Frontiers of China. New York: American Geographical Society, 1940. Reprinted:- Boston: Beacon, 1967.

• 1941: Mongol Journeys. New York: Doubleday Doran, 1941.

• 1945: Solution in Asia. Boston: Little Brown, 1945.

• 1949: The Situation in Asia. Boston: Little Brown, 1949.

• 1950: Pivot of Asia: Sinkiang and the Inner Asian frontiers of China and Russia. Boston: Little Brown, 1950.

• 1950: Ordeal by Slander. Boston: Little Brown, 1950. Reprinted: New York: Carroll & Graf, 2004; introduction by Blanche Wiessen Cook; preface by David Lattimore.

• 1953 The New Political Geography of Inner Asia. Great Britain: The Geographical Journal, Vol. CXIX Part 1, March 1953. Reprinted:- London: William Clowes and Sons, Limited.

• 1962: Nomads and Commissars: Mongolia revisited. New York: Oxford University Press, 1962.

• 1962: Studies in Frontier History: Collected Papers, 1928-1958. London; New York: Oxford University Press; Paris: Mouton, 1962.

• 1964: From China Looking Outward: an inaugural lecture. [Leeds]: Leeds University Press, 1964.

• 1970: History and Revolution in China. Lund: Studentlitteratur, 1970.

By others

• 1944: Eleanor Holgate Lattimore, The Making of Modern China: a short history. New York: W.W. Norton, 1944. Reprinted:- Washington, DC: Infantry Journal, 1944.
• 1947: Eleanor Holgate Lattimore, China: a short history. New York: W. W. Norton, New and rev., 1947.

• 1955: Sh. Nachukdorgi, Nationalism and Revolution in Mongolia. New York: Oxford University Press, 1955.

• 1968: Eleanor Holgate Lattimore, Silks, Spices, and Empire: Asia seen through the eyes of its discoverers. New York: Delacorte, 1968.

• 1990: Fujiko Isono, China Memoirs: Chiang Kai-shek and the War against Japan. Tokyo: University of Tokyo Press, 1990.