In February 2024 Korhonen was elected as the Chairman of the Board of Finnish Institute of International Affairs (FIIA).

[4][5][6] From 2009 to 2013, he was Ambassador of Finland to the Netherlands and Permanent Representative to the Organisation for the Prohibition of Chemical Weapons (OPCW).

Korhonen was President of the international Arms Trade Treaty 2016-2017 (ATT Third Conference of States Parties).

[9] Korhonen delivered Finland's membership application to NATO to Secretary General Jens Stoltenberg on 18 May 2022.

[10][11][citation needed] In 2023, he is part of the North Atlantic Council, as Finland officially joined NATO.