[8] Grégoire has stated that her "childhood was a happy one", noting that she was a good student who made friends easily and loved sports and the outdoors.

She was promoted to an account manager, but after three years of working in advertising, public relations, and sales,[16] she decided to attend radio and television school, where she immediately knew, "I had found my calling".

A lover of culture, arts, and films, when she became aware of an opening at Quebec television station LCN for an entertainment reporter, she applied and was successful in obtaining the position.

[21] Causes she supports include Sheena's Place[21] and BACA, both of which assist those suffering from eating disorders;[14] La Maison Bleue [fr], a drop-in centre for at-risk pregnant mothers;[19] Dove's "Pay Beauty Forward" campaign and Self-Esteem Fund,[22] Girls for the Cure;[21] the Canadian Cancer Society;[23] the Canadian Mental Health Association;[21] the Women's Heart and Stroke Association;[21] and WaterCan.

[21] As part of her work with WaterCan, Grégoire travelled to Ethiopia in October 2006 with her mother-in-law, Margaret Trudeau, who is the honorary president of the organization.

[25] Grégoire is the national ambassador for Plan Canada's "Because I am a Girl" initiative,[21][17][18] and the official spokesperson for The Shield of Athena, which helps women and children dealing with domestic violence.

After the end of the 2015 election, Grégoire Trudeau indicated her preference for the hyphenated surname of "Grégoire-Trudeau", but she switched to using the unhyphenated form in March 2016.

[18] On March 12, 2020, Grégoire isolated herself at Rideau Cottage, along with her husband and children, after she showed flu-like symptoms during the COVID-19 pandemic, shortly after she returned from a speaking engagement in the United Kingdom.

[37][38] On January 18, 2016, Grégoire Trudeau made the impromptu decision to sing a work she composed, titled "Smile Back at Me", at the end of a speech in honour of Martin Luther King Jr. Day at Ottawa City Hall.

[42] In Maclean's, Michael Barclay (formerly a music critic), described the song as "fine", although not designed to be sung a capella, and that Grégoire's voice was "surprisingly strong".