A member of the Socialist Party (PS), he previously served as a Senator for Savoie (2004–2012; 2014) and in government as Minister Delegate for Vocational Training and Apprenticeship (2012–2013) and for European Affairs (2013–2014) under Prime Minister Jean-Marc Ayrault.

[3] Repentin first worked as a parliamentary assistant to MEP Jean-Pierre Cot,[3] before he served as chief of staff to Louis Besson from 1989 to 1995 during the first years of Besson's tenure as Mayor of Chambéry.

Repentin later became an assistant of Besson when he was Secretary of State for Housing under Prime Minister Lionel Jospin from 1997 to 2001.

He served as a member of the Senate, representing the Savoie department, from 2004 to 2012, when he was appointed to the government as Minister Delegate for Vocational Training and Apprenticeship under Prime Minister Jean-Marc Ayrault.

He briefly returned to the Senate in 2014 after Manuel Valls was appointed prime minister.