He was the only author in Belgium to write in the country's three native languages: Dutch, French, and German.

He also taught at the Université libre de Bruxelles, the École d'interprètes internationaux, the University of Mons, INSAS, and the Royal Conservatory of Brussels.

He started journalism in 1971, and worked for the daily newspaper Le Soir, where he directed cultural services from 1985 to 1990.

At the theatre, the pair displayed works by Hugo Claus, Henrik Ibsen, Anton Chekhov, and August Strindberg.

In 1985, De Decker published his first novel, La Grande Roue, which was selected for the Prix Goncourt and translated into several languages.