Guillaume Chabert is an accomplished graduate of Ecole Centrale de Paris, the Paris Institute of Political Studies, and the French Senior Civil Service School (ENA). He began his career in 2000 at the Directorate General for Local Government within the French Ministry of the Interior. In 2004, he transitioned to the Directorate General of the Treasury at the French Ministry of Finance.

In 2010, Guillaume was appointed G20 Project Manager, leading the team that coordinated the 2011 French Presidency of the G20 (and G7/G8) at the French Treasury. After spending two years in Stockholm managing the Regional Department of Economic Affairs for the Nordic countries (Sweden, Denmark, Finland, Norway, and Iceland), he was appointed Adviser to the French Prime Minister in September 2013, overseeing Economy, Finance, and Business. In May 2014, he became the Deputy Chief of Staff for the French Minister of Finance.

By April 2015, Guillaume had advanced to the role of Assistant Secretary for Multilateral Affairs, Trade, and Development Policies at the French Treasury, where he also served as co-chair of the Paris Club and G20/G7 Financial Sous-Sherpa (Deputy's Deputy) for France. Since January 2021, he has held the position of Deputy Director in the Strategy, Policy, and Review Department at the International Monetary Fund.