After completing his Decorative Arts studies in Paris in 1974, Jean-Claude Denis founded the Groupe Imaginon together with Caroline Dillard and Martin Veyron. The collective cooperated on several advertising assignments, before all members went on to pursue individual careers. Between 1975 and 1979, Denis was also active as an illustrator, making covers for the publishing houses Jean-Claude Lattès, Folio, ELP, Fleurus, Robert Laffont and Casterman. He published his first comics pages in the magazine Pilote in 1977. There, he created the series 'André le Corbeau', a series of fairytales in which animals are confronted with human problems, which was collected in three albums published by Dargaud ('Annie Mal', 'La Saison des Chaleurs', 'La Fuite en Avant').
He cooperated with Veyron on an illustrated children's book at Casterman ('Oncle Ernest et les Ravis'), and then made his first solo comic book at Futuropolis in 1978: 'Cours tout Nu'. In a more juvile register, he conceived the series 'Les Aventures de Rup Bonchemin' at Casterman between 1981 and 1983. Also present in À Suivre from 1979, he created the more adult series 'Luc Leroi' in 1980. After several shorter stories, this series soon made its claim to faim in longer albums, like 'Le Nain Jaune' (1985), 'Un Écran de Fumée' (1989), 'Bande d'Individus' (1998) and 'Toutes les Fleurs s'Appellent Tiaré' (2000).
In addition to 'Luc Leroi', Denis made 'Les Sept Péchés' ('The Seven Deadly Sins') in Métal Hurlant in 1982 (an album was published by Les Humanoïdes Associés the following year), and he cooperated on several collective projects. During a stay at the isle of La Réunion, he made 'Bonbon Piment' for Éditions du Bout du Monde. Upon his return in France, he reworked the album with several short stories published in Corto in 1988-89, and a new album was published by Albin Michel in 1991. Also, he made several comics for L'Écho des Savanes starting in 1990: 'L'Ombre aux Tableaux' (1990), 'Le Pélican' (1994), and 'Drôles d'Oisifs' (1995). In 1992, he illustrated 'Le Guide des Jeux d'Argent' for Éditions la Sirène, and subsequently pursued the children's fairytale 'L'Île aux Mainates' at Albin Michel.
In addition to comics, Denis made water paintings for 'Les Rameaux de Jéricho' by Ibrahim Souss in 1994, and two years later, he made the music and the pastels for 'Le Cri des Sirènes', a CD-book published by Seuil Jeunesse. For this same publisher, he also made a couple of illustrated children's books, such as 'Un Artiste de Chat' (1998) and 'Tête de Mule' (2000). He illustrated 'Les Trains de Plaisir' in the collection Les Correspondances de Pierre Cristin at Dargaud, as well as 'Bande à Part' by Jerome Charyn at Gallimard Jeunesse. In 2002, he published the comic 'Quelques Mois à l'Amélie' in the Aire Libre collection of publisher Dupuis. The story is about the writer Aloys Clark, who is working on a manuscript, and this manuscript was equally published by PLG. Also for the Aire Libre collection, he made 'La Beauté à Domicile' in 2004.