Carlo Thelen joined the Luxembourg Chamber of Commerce in 1996 as Economic Advisor.

In 2003, he became a member of the Chamber's Executive Committee, and in 2004, Director of International Affairs. In 2014, he was appointed CEO, general manager.

Until 2019, he also served as the Chamber's Chief Economist, preparing and presenting the Chamber's opinion on the state budget each year. Carlo Thelen is additionally the author of a notable expert blog highlighting important socio-economic issues of the day, and of articles published by the Chamber of Commerce. He also represents the Chamber of Commerce on various working groups and councils within Luxembourg institutions and organizations. In addition to his economic expertise, Carlo Thelen has extensive experience in commercial and economic advocacy, and participates in economic missions abroad where he promotes the Grand Duchy's economy and businesses.