Catherine Muler, also known as Cathy Muller, Catel Muller or simply Catel, studied at the School of Applied Arts in Strasbourg, where she graduated in 1990. She specialized in children's illustrations, working mainly with the publishers Nathan, Epigones and Hachette.
In 1996, she created her first stories that featured the characters 'Bop et Flop' in cooperation with Paul Martin for the monthly magazine 'Images Doc' (Bayard Presse).
Since 1999, she has illustrated the series 'Marion & Charles', based on two novel characters by Fanny Jolly. In 2000, she began the series 'Lucie' with writer Véronique Grisseaux in Les Humanoïdes Associés' Tohu Bohu series (continued by Casterman after 2003). Together with scriptwriter Sophie Dieuaide, she started 'Les Papooses', also for Casterman in 2003. In the following year, she wrote the more adult World War I comic 'Le Sang des Valentines' for Christian De Metter.
Catel won the Prix Essentiel and RTL Grand Prix at the Angouleme Festival for KIKI.