A graduate of the Sorbonne in political communications, Zélia Césarion began her career in 2010 as a communications officer and then press attaché in the office of the Minister for Housing. Two years later, she joined the French National Assembly as a parliamentary assistant to the former Minister for Housing, now member of parliament for Marne. At the same time, she served as Deputy Secretary General of the French Association of Parliamentary Assistants (AFCP), with responsibility for communications. In May 2017, she was appointed Press Advisor to the Prime Minister, overseeing media relations and communications. 

She joined SNCF Réseau in 2020 as Executive Assistant to the Chair. Since 2023, she has also served as Director of Media Relations.