Alexia holds an LL.B. in civil law from the Faculty of Law of the University of Sherbrooke, and an LL.M. in public international law from the University of Utrecht. She specialized in international human rights law, examining how international and regional institutions protect the rights of vulnerable people and marginalized communities. Alexia Legault developed a strong interest in the protection of sexual and reproductive rights, writing her master's thesis on the right to abortion.

During her studies, Alexia worked as a human rights officer at the Canadian Human Rights Commission, where she analyzed and processed complaints of discrimination in the prison, banking, transportation and law enforcement sectors. She completed her articleship at the Bar as part of a defense team at the International Criminal Court in The Hague before joining the legal team at Lawyers Without Borders Canada in Quebec City.