[2] A third by-election was pending in the riding of Haldimand—Norfolk following the resignation of Conservative MP Diane Finley on May 20, 2021, but was cancelled due to the 2021 Canadian federal election being called for September 20, 2021.

Prime Minister Justin Trudeau announced both by-elections on Friday September 18, along with Liberal candidates for each riding.

[5] Annamie Paul, the newly elected leader of the Green Party and Green candidate for Toronto Centre, called on the government to delay the by-elections, citing increased restrictions on movement and activity in Toronto in light of rising cases of COVID-19.

[6] Trudeau rejected changing the schedule, saying that the by-elections have to be held within a certain time period of the seats becoming vacant, and that the pandemic may be worse later in the year.

[7] Any changes to by-election dates would be approved by the cabinet, but would have to first be proposed by the independent Chief Electoral Officer.

By September 7, five candidates had launched their campaigns for the Liberal nomination including 2019 Thornhill candidate Gary Gladstone, former chief fundraiser of the provincial Ontario Liberal Fund, Bobby Walman, as well as former Canadian Jewish News editor Yoni Goldstein.

[citation needed] The Conservatives ultimately nominated Julius Tiangson, who previously ran for the party in Mississauga Centre in 2015.