This article questions the implications of a shift in dominant urban planning framework from sustainable development to climate change. The case of the City of Vancouver’s Greenest City Action Plan (GCAP) (2010–2020) is investigated as a window to perceive and understand this shift. We begin with the stance that the primary implications of a shift from sustainability to climate change policy are in social and institutional learning about action, and as such we adopt an urban knowledge order framework for our analysis. At the organizational scale, we investigate the implications of GCAP in terms of its impact on the city structure and organization, in terms of the way it works with the public and with external organizations in designing and implementing policy, and in terms of reporting and accountability. An understanding of the construction of an urban knowledge arena as a valuable process and outcome of sustainability and climate policy work offers a pragmatic way to integrate and promote sustainability thinking across the city administration, amongst citizen-participants, and in collaboration with external partners. We see in the City of Vancouver an ecologically modernizing city, which is also learning a new, partnership-based way of wielding power and coordinating and justifying sustainability and climate change policy and action.