[3] Born in Lille in 1987, Toussaint is the daughter of a sailor and a professor of economics in technical high school, both involved in the International Movement ATD Fourth World.

At the same time, she volunteered for the Yasuní-ITT Initiative, launched by Ecuadorian President Rafael Correa for the preservation of Yasuni National Park.

In addition to her committee assignments, Toussaint is part of the Parliament's delegations for relations with the United States and to the Euro-Latin American Parliamentary Assembly (EuroLat).

[17] Since the 2024 European Parliament election, Toussaint has been serving as deputy chairwoman of the Greens–European Free Alliance (Greens/EFA) group, under the leadership of co-chairs Terry Reintke and Bas Eickhout.

[18] In May 2021, Toussaint joined a group of 39 mostly Green Party lawmakers from the European Parliament who in a letter urged the leaders of Germany, France and Italy not to support Arctic LNG 2, a $21 billion Russian Arctic liquefied natural gas (LNG) project, due to climate change concerns.