Following his admission to the Quebec Bar, Chrétien entered the Legal Affairs Bureau of the Department of External Affairs and the Department of Foreign Affairs in 1966.
His positions include:
- Republic of the Congo: 1978–1981
- Mexico: 1985–1988
- Belgium: 1991–1994
- United States: 1994–2000
- France: 2000–2003
From 1988 to 1991, he was associate under secretary of state for external affairs. In 1996, he was named special envoy to the UN for the Great Lakes and Central Africa.
In 2004, he joined the law firm Fasken Martineau DuMoulin and in December 2005, joined the Pierre Elliott Trudeau Foundation. Since April 2004, he is Chairman of the board of the Center for International Studies of the Université de Montréal (CÉRIUM). He was appointed an Officer of the Order of Canada in 2010.