After studying as an undergraduate at the University of Oslo, Westad attended the University of North Carolina at Chapel Hill to work on his Ph.D under Professor Michael H. Hunt. He was appointed Director of Research at the Norwegian Nobel Institute and Adjunct Professor of History at the University of Oslo in 1991. In 1998, he left Oslo to join the International History Department at the LSE, where he also worked in the LSE Asia Research Centre before becoming Head of Department in 2003.