Pierre Le Guen started out working for the magazine O.K. after winning a contest held by this magazine in 1946. Between 1947 and 1949 he made his professional debut with the series 'Tangor'. He also cooperated on the second series of Pic et Nic, and worked as the assistant of René Brantonne for a while. In 1950 he joined the team of Vaillant. For this magazine, he created 'Jacques Flash' with Jean Ollivier (1956-59) and took over series like 'Hourrah Freddi' (1950-53) and 'Nasdine Hodja' (1953-69). He was also present in Coq Hardi and Mireille, producing 'L'Orpheline du Cirque' with a script by Jacques François (Marijac) from 1953, as well as in Pierrot with 'Envoyé Spécial' (script by Lucien Bornert).
He worked for the publishing house Fleurus all through the 1970s, making series like 'Frank et Drago' in Formule 1 and 'Capitaine Enfer' in Pieds Nickelés Magazine. With Christian Godard, he created 'La Vie d'Artiche' in Circus in 1978. He was head of the Five Stars studios in the early 1980s, where he worked with fellow studio members Christian Gaty, Philippe Luguy, René Deynis and Max Lenvers on comics adaptations of television series like 'Albator' for the magazine Le Journal de Cap'tain Fulgur' by Dargaud. Le Guen has also done a lot of illustration work for the juvenile press, among others for Rouge & Or, Hachette Junior and L'Archer Vert.