This chapter examines the evolution of relations between Québec and U.S. states over the past 20 years on the issue of climate change. Through the case studies of the New England Governors and Eastern Canadian premiers, as well as the Western Climate Initiative, the authors illustrate that cooperation between Québec and its U.S. counterparts has been not only maintained but also strengthened over time. Shared energy and environmental interests (notably the export of hydroelectricity), along with similar constitutional powers and the institutionalization of these cooperative bonds, partly account for why, despite the political shifts of the last two decades, Québec's climate paradiplomacy with the U.S. states has been maintained without disruption.