Academics and practitioners have responded to the gridlock in the international climate-change regime by more actively exploring the ability of individuals and/or groups of states to fill in the associated 'governance gaps' by engaging in policy innovation at the level of the nation state, including its regional and local emanations. Here, we draw together the findings of a collection that, for the first time, explores policy innovation at this level from three key perspectives: the source of new policy elements ('invention'), their wider entry into use ('diffusion'), and their projected and/ or real effects ('evaluation'). After critically reviewing the findings of the contributions from these perspectives, we explore new directions for definitional, conceptual-theoretical, and empirical work in this field. Finally, we explore how a more systematic analysis of policy innovation dynamics can inform a much fuller understanding of climate policy and governance across different sites and scales.