Ysebaert obtained a Master's degree Diplomacy at the University of Ghent in 1972.
After having worked for a short period at the VRT, the public Flemish broadcaster, Ysebaert joined the cabinet of the liberal minister of National Education Herman De Croo from 1974 to 1977.
When the Liberals subsequently ended up in the opposition, Ysebaert started working for the Party for Freedom and Progress (PVV) at the study service and later as spokesperson.
From 1985 to 1989 Ysebaert became chief of staff for Frans Grootjans, Guy Verhofstadt and Ward Beysen.
Afterwards, he held several board positions at NMBS, SABENA and Het Laatste Nieuws, among others.