Whereas his father, Louis Joxe, was Justice Minister of Charles de Gaulle, Pierre Joxe entered politics as a follower of François Mitterrand, first in the Convention of Republican Institutions, then (from 1971) in the renewed Socialist Party (PS).

Considered one of the closest allies of the PS leader, he was elected as a deputy for the Saône-et-Loire département in 1973.

In 1981, when Mitterrand was elected President of France, Joxe became Minister of Industry for only one month, before he became leader of the Socialist group in the French National Assembly.

Re-appointed leader of the PS parliamentary group again, he became the Interior Minister after Mitterrand had won a second presidential term in 1988.

During March 1993, Joxe gave up politics to lead the Court of Audit of France.