A member of the French socialist party, Isabelle Thomas has been an MEP since June 2012. She is a member of the Committee on Fisheries and of the Committee on Culture and Education.
Isabelle Thomas began her political career in 1983 in the anti-racist and unionist movement. She was noticed by François Mitterrand during the 1986 movement. After his re-election, he appointed her to Special Advisor to the President on Youth Affairs.
In 1993, Isabelle Thomas moved to Brittany and became Town Councillor of Saint-Malo, as well as Regional Councillor. She presided over the Environment and Quality of Life Committee from 2004 to 2010. In 2010, the President of the Brittany Region, Jean-Yves Le Drian, made her Vice-President in charge of the Sea and Coastal Protection.
Within the Socialist Party, she is heading the National Secretariat for Maritime Affairs.