Lars van Dassen has worked in the nuclear non-proliferation and security field for more than 30 years. His academic background is in international relations and political science. From 1993 till 2001, he was a scholar at the Peace Research Institute Frankfurt and the Department for Peace and Conflict Research at Uppsala University.

In 2001, he joined the Swedish Radiation Safety Authority (SSM) and became responsible for the implementation of international projects primarily in the field of nuclear security in Ukraine, Russia, Kazakhstan, Georgia, Moldova and the Baltic States. Since 2008, he has served as Acting Department Head, Section Head and Director for the Office for External Relations at SSM. He was sous-sherpa for Sweden at the Nuclear Security Summits held between 2010 and 2016.