[3] Before entering federal politics, Weir ran in the 2013 Saskatchewan New Democratic Party leadership election and was an economist with the Canadian section of the United Steelworkers union.

[5] Weir began his career in Canada’s federal public service and went on to work as an economist with the Canadian Labour Congress, the United Steelworkers and the International Trade Union Confederation[6] After completing his term in Parliament, Weir worked as a consultant, served as Senior Economist with the Alliance of Canadian Cinema, Television and Radio Artists (ACTRA), and wrote opinion[7] pieces[8] for The Globe and Mail national newspaper.

In May 2012 while Weir was an economist working with the United Steelworkers and presenting in front of the Parliamentary Finance committee, he was questioned by Conservative MP Randy Hoback – who asked "Are you now, or have you ever been, a member of the NDP party[sic]".

[10][11] In 2004, Weir ran in the federal riding of Wascana against Liberal finance minister Ralph Goodale as the New Democratic Party's candidate, but was defeated.

[4] In June 2012 a group of Canadian economists sent a public letter calling on Erin Weir to enter the 2013 Saskatchewan New Democratic Party leadership election.

His campaign was described by the media as organized[18] and one of the main political commentators in the province said the race was "highly competitive"[19] and "The fact they could all win is probably incentive for all four to run.

[24] Although internal debate about this proposal was characterized as “harassment,”[25] carbon border adjustments subsequently appeared in the 2020 fall economic statement[26] and 2021 federal budget.

"[25] As an independent member, Weir asked Speaker Geoff Regan to have his affiliation switched to the Co-operative Commonwealth Federation (CCF), the predecessor of the modern NDP.

[33] Former Saskatchewan NDP Finance Minister Eric Cline wrote in the National Post that "Weir had engaged in conduct described by an investigator as “on the low-end of the scale".

After completing his term in Parliament, Weir worked as a consultant, served as Senior Economist with the Alliance of Canadian Cinema, Television and Radio Artists (ACTRA), and wrote opinion pieces for The Globe and Mail national newspaper.