Jacobsen was born in Oslo. He started off his career with the Labour newspaper "Dagsavisen" (then "Arbeiderbladet"). He was a journalist for "Arbeiderbladet" from 1967 to 1977 and editor-in-chief in presses from 1977 to 1990. Furthermore, he was the main editor-in-chief of "Arbeiderbladet" from 1991 to 1994. Later, he was the information director for the Norwegian Bar Association from 1994 to 2003.