Alexander Kmentt started his career at the Austrian Federal Ministry for European and International Affairs in 1994, serving in various offices, including in the Department for International Organisations, the Department for Humanitarian and Refugee Affairs. He held a six months position at the Austrian Embassy in Prague, Czech Republic. in 2005 and was later appointed Deputy Director of the Department for Disarmament Affairs and Head of the Unit for Nuclear Issues (IAEA, CTBT, NPT, NSG).
For the period between 2006 and 2011 Kmentt was the Special Assistant to the Executive Secretary of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO).
Alexander is the former Director for Disarmament, at the Arms Control and Non-Proliferation division and, since 2011, has served as Ambassador to the Austrian Ministry of Foreign Affairs.