Born Joseph Gillain in Gedinne, Namur, he completed various art studies (woodcraft, goldsmithing, drawing and painting) at the abbey of Maredsous.

After the war, he handed over his existing series' to younger artists: André Franquin got Spirou et Fantasio, Eddy Paape Jean Valhardi and Victor Hubinon Blondin et Cirage.

He also had a few young cartoonists living with him in his studio in Waterloo, thus creating the so-called "School of Marcinelle": this included André Franquin, Morris, and Will.

Later students of Jijé, not really working in the Atom style or the School of Marcinelle, include Jean Giraud (aka Moebius), Jean-Claude Mézières and Guy Mouminoux.

Tibet, author of Ric Hochet and Chick Bill, and for the major part of his career working for rival Tintin magazine, has said that "If Hergé is considered as God the Father, then Jijé undoubtedly is the Godfather".

[2] In his writing, he can be seen as a transitional figure between the classic hero-driven comics like Alix or Michel Vaillant, and the modern anti-heroes like Blueberry or the works of Hermann Huppen.

His illustrations for stories like The Count of Monte Cristo (in the Belgian magazine Bonnes Soirées with René Follet) mix elements from his comic work and his paintings into one decorative style.