Born in Washington, DC, Poirson's mother was a paintings conservator and restorer and her father a computer consultant for the World Bank.

[2] Poirson's professional career began in London, where she was a legislative assistant to a Labour Member of Parliament[3] and researcher at Nesta for about two years.

In 2012, Poirson and her partner created the CITRIX sustainable urban development working group, of which Hubert Védrine, Brice Lalonde and Sam Pitroda are stakeholders.

In this role, she worked on drinking water distribution projects in the slums of large Indian megacities, particularly in Karnataka and Nagpur.

[6] Poirson returned to France in 2016 to engage in Emmanuel Macron's newly-launched political movement, En Marche!

[8] Upon taking office, Hulot announced that Poirson would be in charge of policies related to the sea, biodiversity and the ocean; he would also delegate her the questions discussed at a European level.