Vollebæk's diplomatic career includes assignments to New Delhi, Madrid and Harare. He was Norwegian Ambassador to Costa Rica in 1991–1993 and Assistant Secretary General at the Norwegian Ministry of Foreign Affairs from 1994 until he became Foreign Minister in 1997. He served as Deputy Co-Chairman of the International Conference on the Former Yugoslavia in 1993.
He was appointed Primus inter pares of the Panel of Eminent Persons on Strengthening the Effectiveness of the OSCE in 2005. He was Chairman of the Council of the Baltic Sea States in 1999–2000 and Chairman of the Barents Euro-Arctic Council in 1997–1998. Between October 1989 and November 1990, he was the Deputy Minister for Foreign Affairs of Norway.