Jeroen Janssen studied at the Saint-Luc art institute in Ghent. He began drawing comics while living and working as an art teacher in Nyundo, Rwanda, from 1990 to 1994. His first long comic story, 'Muzungu, Sluipend Gif in Rwanda', was published by Wonderland in Hasselt in 1997. This book about the civil war in Rwanda received the VSB-award during the Haarlem comics festival of in 1998.
Janssen made most of his following books with writer Pieter van Oudheusden, who was in the jury of the VSB Award. After the graphic novel 'Een Nachtegaal in de Stad' (1999) and the story collection 'Klaarlichte Nacht' (2001), Janssen and Van Oudheusden drew inspiration from fables and African folktales for 'Bakamé' (2003), 'De Grote Tovenaar: De kruisweg van Mpyisi' (2007) and 'De Wraak van Bakamé' (2010).
In 2013, Janssen made an drawn report on 'Doel', a Flemish ghosttown that is threatened with complete demolition due to the planned enlargement of the harbour of Antwerp. Short stories by Janssen have appeared in magazines like Beeldstorm, Stripburger, Incognito, Kerozene, Parcifal, Ink and Zone 5300. He works part-time in a library, is freelance illustrator and does the coloring of 'Hippo & Zeno', a comic by Klaas Verplancke.