He was member of the Belgian Chamber of Representatives (1965–1974 and 1977–1989) and senator in the Belgian Senate (1974–1977) for the PRL and was President (1981–1988) of the Belgian Chamber of Representatives of public work (1974–1976).
In 1983, Jean Defraigne was appointed as minister of state.
From 1989 to 1994 Defraigne served as a Member of the European Parliament, where he sat with the Liberal, Democrat and Reformist Group.