Upon appointment, Dyck wished to sit as a New Democratic Party senator, but NDP spokesperson Karl Belanger immediately indicated that the party would not recognize her as a member of the NDP caucus: as the party platform specifically favours abolition of the Senate, it refused to confer legitimacy on the body by accepting Dyck; additionally, Dyck's membership in the NDP was revealed to have lapsed. Under the rules of the Senate, senators are free to designate themselves however they see fit, and Dyck changed her designation to say Independent New Democratic Party. On January 15, 2009, she joined the Liberal Senate caucus.
On January 29, 2014, Liberal Party leader Justin Trudeau announced all Liberal Senators, including Dyck, were removed from the Liberal caucus, and would continue sitting as Independents. According to Senate Opposition leader James Cowan, the Senators will still refer to themselves as Liberals even if they are no longer members of the parliamentary Liberal caucus.
In 2014 Dyck accused Conservative MP Rob Clarke, who is also native, of "behaving like a white man" by pushing the Indian Act Amendment and Replacement Act. She later said she recognized the comment could be hurtful.