He was Professor of Medieval History, University of Liverpool (1945–1956) during which period he lived in the Seneschal's House, Halton Village, Stevenson Research Professor, University of London (1956–1962), University of California (1965–1968) and Professor of History, Brandeis University (1968–1970 and 1972–1981). He was Chichele Professor of Modern History, University of Oxford from 1970 to 1973.
During the Second World War, Barraclough's sympathy for the USSR and public opposition to the Warsaw Uprising of 1944 drew the criticism of George Orwell, among others.
Professor Barraclough began his career as a medievalist, but developed into a contemporary global historian. He was deeply concerned about history's uses and relevance in the 20th century. It seemed to him that political debate and ultimately political decisions, suffered from a lack of historical insight. To rectify this problem Barraclough developed historiographical methods for comparative history.
By anchoring study of the past at the origins of a historical investigation, while simultaneously researching contemporary areas most directly connected to that anchor research, his methods established comparisons between past and present. With this two-pronged research structure, Barraclough was able to organize his investigations by looking from the past forward and from the present backwards. He sought historical threads that connect past to present while also observing the discontinuities that separate past from present.
In his writing, Barraclough turned to geography, social and economic cycles, empires, trade and tribes as historical units he felt most clearly connect past to present or combine to end that continuity. Using these methods allowed him to sketch an outline of world history, identifying its ups, downs and turning points.
His first two books on historiography, History in a Changing World and An Introduction to Contemporary History are collections of essays. With scholarly authority, Barraclough served as editor of The Times Atlas of World History, which continues to be revised.
- Public Notaries and the Papal Curia (1934)
- Papal Provisions: Aspects of Church History Constitutional, Legal and Administrative in the Later Middle Ages (1935)
- Factors in German History (1946)
- Origins of Modern Germany (1947)
- Mediaeval Germany 911 - 1250 (1948) essays by German historians, translator
- Crown, Community and Parliament in the Later Middle Ages: Studies in English Constitutional History by Gaillard T. Lapsley (1951) editor with Helen M. Cam
- History in a Changing World (1955)
- Survey of International Affairs, 1955-1956 (1960) with Rachel F. Wall
- Social Life in Early England (1960)
- Survey of International Affairs, 1956-1958 (1962)
- European Unity in Thought and Action (1963) Vogelenzang Lecture
- Survey of International Affairs, 1959-1960 (1964)
- An Introduction to Contemporary History (1964)
- The Mediaeval Empire - Idea and Reality (1964)
- The Historical Association, 1906-1966 (1967) Presidential Address
- The Medieval Papacy (1968)
- Eastern and Western Europe in the Middle Ages (1970)
- The Crucible of Europe: the Ninth and Tenth Centuries In European History (1976) later as The Crucible of the Middle Ages
- The Times Atlas of World History (1978)
- Main Trends in History (1978)
- The Turning Points in World History (1979)
- The Christian World: A Social and Cultural History of Christianity (1981)
- The Times Concise Atlas of World History (1982)
- From Agadir to Armageddon: Anatomy of a Crisis (1982)
- Charters of the Anglo-Norman Earls of Chester, c.1071-1237 (1988)
- Atlas of World History (1989) with Norman Stone, and later editions and atlases
- The Times History of the World (2001) with Richard Overy
- Woodland, Jenny (2011). Bootham School Register. York, England: BOSA.
- A. J. P. Taylor (1983) A Personal History, p. 106, Coronet Books ISBN 0-340-35471-2
- Encyclopedia of historians and historical writing, Volume 1