The son of Charles Embleton Barrow and Marjorie née Stuart, he was born on 28 November 1924, at Headingley near Leeds. Barrow attended St Edward's School, Oxford, and Inverness Royal Academy, moving onto the University of St Andrews and Pembroke College, Oxford.
He became lecturer in history at University College, London in 1950, remaining there until 1961 when he became professor of medieval history at the University of Newcastle upon Tyne, and then in 1974, professor of Scottish history at the University of St Andrews. He was Sir William Fraser Professor of Scottish History and Palaeography at the University of Edinburgh from 1979 to 1992.
He married, in 1951, Heather Elizabeth née Lownie, with whom he had one son and one daughter.
He began his work by studying the nature of feudalism in Anglo-Norman Britain, but moved on to specialize more thoroughly on Scottish feudalism. His work tended to focus on Normanisation in High Medieval Scotland, especially in reference to governmental institutions.
Barrow's more notable publications include:
- Feudal Britain, (London, 1956).
- Robert Bruce and the Community of the Realm of Scotland, (Edinburgh, 1965; 4th edn., 2005).
- The Kingdom of the Scots, (London, 1973), a collection of his scholarly articles.
- Editor of The Scottish Tradition, (Edinburgh, 1974).
- The Anglo-Norman Era in Scottish History, (Oxford, 1980).
- Kingship and Unity: Scotland, 1000–1306, (London, 1981).
- Scotland and its Neighbours in the Middle Ages, (London, 1992) - another collection of his scholarly articles.
Editions of texts
- Editor of Acts of Malcolm IV, 1153–1165, (Edinburgh, 1960) - Regesta Regum Scottorum, vol. i.
- Co-editor (with W.W. Scott) of Acts of William I, 1165–1214 (Edinburgh, 1971) Regesta Regum Scottorum, vol. ii.
- Editor of The Charters of King David I, (Woodbridge, 1999).
- Barrow, G.W.S. 'Earls of Fife in the 12th Century', (Proceedings of the Society of Antiquaries of Scotland, 1952–53), pp. 51–61.
- Barrow, G.W.S. 'Religion in Scotland on the eve of Christianity' in Forschungen zur Reichs-, Papst- und Landesgeschichte, ed. Borchardt and Bunz (Stuttgart 1998) 25-32.
- "BARROW - Deaths Announcements". Announcements.telegraph.co.uk. 2013-12-14. Retrieved 2013-12-18.