From 2011 to 2015 he was the Secretary General of the Organization for Security and Co-operation in Europe, and from 2015 to 2024 he was a judge at the International Criminal Court (ICC) in The Hague.

In 1986, he moved to Washington, D.C., where he worked as cultural Counsellor for the French Embassy, returning to Paris in 1988 as Principal Adviser to Defense Minister Jean-Pierre Chevenement.

From 1991 to 1994, de Brichambaut was the head of French Delegation at the Conference on Security and Co-operation in Europe (later (OSCE) in Vienna.

In his capacity as presiding judge of Trial Chamber VII in 2016, he convicted former vice-president of the Democratic Republic of the Congo Jean-Pierre Bemba and four members of his legal team of interfering with witnesses; the verdicts marked the first time the court found suspects guilty of attempting to "pervert the course of justice", a concept from British law parallel to obstruction of justice in American law.

[6] In a high-profile decision on South Africa’s failure to arrest and surrender President Omar Al-Bashir of Sudan to the Court while he was on its territory, de Brichambaut issued a separate opinion in 2017, deciding that as signatories to the Genocide Convention both countries were obligated to arrest Bashir.