Gaël Séjourné was born in St. Nazaire, and studied Plastic Arts in Rennes. He had his first job as a graphic artist with the Sablaise publishing house in Les Sables d'Olonne in 1988. During his period, he offered his caricatural and humorous comics to several publishers. He had his first break after teaming up with Serge Perrotin and changing his style from caricatural to realism. This resulted, thanks to the guidance of Didier Crisse, in the 'Lance Crow Dog' series, that started at Le Téméraire publishers in 1998. Five books were eventually published until 2005, the final three by Soleil Productions.
'Lance Crow Dog' was followed by 'Tatanka', a detective thriller in cooperation with Joël Callède and published by Delcourt from 2005 to 2009. Séjourné and Callède subsequently started their next project for Vents d'Ouest, 'L'Appel des origines'. Séjourné has also drawn an installment in the alternative history series 'Jour J' by Jean-Pierre Pécau, Fred Duval and Fred Blanchard (Delcourt, 2010).