Born in Granby, Quebec, and educated in Magog, Dusseault is the son of a daycare administrator and a customer service manager.

[3][4] Dusseault was a first-year student studying applied politics at the Université de Sherbrooke at the time of his election as an MP.

[2] As a New Democratic Party candidate in the riding of Sherbrooke, Dusseault defeated the incumbent Bloc Québécois MP Serge Cardin (four decades Dusseault's elder), and was elected at the age of 19 years, 336 days, making him the youngest Canadian ever to be elected to the House of Commons, surpassing former Liberal Party MP Claude-André Lachance, who was aged 20 years, 94 days when elected in 1974.

He was elected in the same election as five McGill University students, fellow NDP MPs Charmaine Borg, Matthew Dubé, Mylène Freeman, Laurin Liu, and Jamie Nicholls, following the NDP's unexpected mid-campaign surge in Quebec.

[5] Dusseault voted for the first time in this election and had originally planned to work a summer job at a golf course but served in Parliament instead.