Quatennens became interested in politics at the age of 15 in 2006, when there were big demonstrations against a new labour law in France. He joined charities to help homeless people and became a member of the Attac organization. In 2006, he got the high scool diploma in a Catholic high shool in Bondues, Nord. He started studying economics at the University of Lille but failed exams in second year. Then he got a technical diploma and worked as a customer adviser for the energy company EDF.