Taksøe -Jensen has been the Assistant Secretary-General for Legal Affairs at the UN since 2008. From 2004 to 2008, he was the Head of the Legal Service in the Danish Ministry of Foreign Affairs and the principal legal adviser to the Danish Foreign Minister on all matters concerning international law. He joined the Danish Ministry of Foreign Affairs in 1987 and has served in the Legal Service of the Ministry since 1999, including as Head of the Department of International Law, Security Policy Department, the European Union Law Department and other various government commissions. He has also served at the European Court of Human Rights (2004-2008), the Court of Conciliation and Arbitration within the Organisation for Security and Cooperation in Europe (OSCE) and Chairman of the Commission on the Red Cross of the Government of Denmark (2007-2008).
Additionally, Taksøe -Jensen has been posted in Vienna, at the Danish Embassy and with the Danish Delegation to the Treaty on Conventional Armed Forces in Europe/Confidence and Security-Building Measures (CFE/CSBM); and to Brussels as a Danish representative to the European Union. Between 1999 and 2008, he lectured at numerous courses on EU law, procedures, techniques, policies and negotiations.