[1][2] Hawthorn studied at Jesus College, Oxford (BA) and the London School of Economics and Political Science (MA).
In 1970 he began a longstanding academic association with the University of Cambridge: lecturer in Sociology, 1970–1985; reader in Sociology and Politics, 1985–1998; professor of International Politics, 1998–2007; fellow, Churchill College, 1970–1976; fellow, Clare Hall since 1982.
According to Stefan Collini in Hawthorn's obituary at The Guardian: "It is thanks to him more than to any other individual that Cambridge now boasts a flourishing Department of Politics and International Studies".
He was a member of the editorial board of the Cambridge Review of International Affairs.
Hawthorn was also the author of numerous papers in learned journals and other periodicals.