Isabelle Bourgeois started playing French horn at the age of 8. At the age of 13, she was awarded the Gold Medal of the Conservatoire de Montbéliard in the class of her father, Jean-Marie Bourgeois, then the Gold Medal of the Conservatoire de Besançon in the class of Walter Bellagamba. In the same year she passed the entrance exam to the Paris National Conservatory and in 1987 she was awarded First Prizes in horn and chamber music. She then went on to perfect her skills at the Hochschule d'Essen in the class of Hermann Baumann.
Isabelle Bourgeois joined the horn section of the Orchestre de la Suisse Romande in 1989 and in 1993 she was appointed substitute soloist.