Matriculating from Reykjavík Junior College in 1964 and graduating in Law (cand. jur.) from the University of Iceland in 1971, Björn was active in student politics and after graduation worked as a publishing director of Almenna bókafélagið from 1971 to 1974. As foreign news editor he worked at daily Vísir in 1974, as Deputy Secretary General in the Prime Minister's office from 1974 to 1975.
Björn worked in the Prime Minister's Office from 1975 to 1979, as a journalist on Icelandic daily Morgunblaðið from 1979 to 1984 and as deputy editor of Morgunblaðið from 1984 to 1991. Björn attended the Bilderberg Group conference in 1988, 1991, 1993 and 1995.