After his army service (1981–1982) he started working as a spokesperson to the then secretary of state Annemie Neyts.

When Verhofstadt is called to become vice-premier he takes Vanhengel with him to work on his staff (1985–1988).

In 1988, Guy Vanhengel became manager of Tourism Flanders and was then sent on secondment with the cabinet of Patrick Dewael who held the office of minister of Cultural Affairs (1988–1989).

In 1995, Vanhengel turned member of the Brussels Parliament, later to become minister in the Brussels government (2000) annex minister in the Flemish Community Commission – Vlaamse Gemeenschapscommissie and the Common Community Commission -Gemeenschappelijke Gemeenschapscommissie.

Vanhengel was the man for the job and for a couple of months (2002–2003)held a post in both the Brussels and the Flemish Government.