Trade negotiations address issues that are increasingly pertinent to substate governments, leading many to insist on being included in trade negotiations. The increasingly multilevel nature of trade negotiations and the influence of substate governments in the negotiation process is beginning to attract theoretical attention. The Canadian case is interesting here as it allows us to test two recent theories about the role of substate governments in trade negotiations. Canadian provinces are increasingly included in trade negotiations despite the fact that they do not have veto power and the Senate of Canada does not represent their interests. The Canadian case demonstrates that, contrary to the means-of-influence theory, inclusion in the negotiation process is more important than formal constitutional powers. Moreover, contrary to a recent theory that questions the joint-decision trap perspective, in the case of the NAFTA renegotiation, granting veto power to the provinces would likely have been a major problem for Canadian negotiators. This article compares the role Ontario and Québec played in the NAFTA renegotiations with their role in CETA and Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP) negotiations.