This article explores the contradictions in the Canadian Auto Workers Union’s (CAW) approach to environmental issues, particularly climate change. Despite being one of the Canadian labor movement’s leading proponents of social unionism— understood as a union ethos committed to working-class interests beyond the workplace, and a strategic repertoire that involves community-union alliances— the CAW’s environmental activism demonstrates the contradictory way that social unionism can be understood and practiced by unions. Through a critical discourse analysis of CAW policy documents and leadership statements, we show the union has not reframed its bargaining demands to emphasize both economically and environmentally sustainable production. Instead, the CAW’s relatively uncritical defense of the North American auto industry and the jobs it provides, despite the clearly negative role such production plays in the climate crisis, its acceptance of the structures of automobility, and its emphasis on environmental issues that have little to do with the nature of their industry, indicates the way that social unionism can be an add-on rather than a fundamental reorientation of a union’s role and purpose. We argue that, for social unionist environmental activism to be effective, the CAW must incorporate social unionist goals and analyses into their bargaining priorities, and confront the contradictions between their members’ interests as autoworkers, on the one hand, and as workers and global citizens who require economically and environmentally sustainable livelihoods, on the other.