From 1974 to 1980, Nordmann was an elected member of the Grand Council of Fribourg, the legislature of the canton of Fribourg, in Switzerland.[5]
He then joined the Swiss Department of Foreign Affairs and in 1984 he was made ambassador to Guatemala, Costa Rica, Honduras, Nicaragua, Salvador et Panama. In 1987, he became head of the Swiss delegation to UNESCO. He then headed the International Organizations Directorate of the Swiss Department of Foreign Affairs. Starting in 1994, he became the Swiss ambassador to Great Britain. In 2000, he became the permanent representative of Switzerland to the United Nations in Geneva. He fought for the maintenance of the GATT (now the World Trade Organization) in Geneva. He was the Swiss ambassador to France from 2003 to 2007. There, he collaborated with the French authorities to hold the G8 summit in Evian.[6][7][8][9][10]
In 2022, he started writing a regular column on foreign affairs for French-language newspaper Le Temps.[14] Nordmann is regularly quoted in Swiss news media for his analysis of foreign affairs.[15][16][17][18][19]