Scholars have undertaken much conceptual development of “polycentric” climate governance (PCG). Yet, there has been limited empirical examination of whether this descriptive, analytical, and normative concept can aid climate change mitigation; it may even undermine our efforts in certain contexts. Thus this special issue examines the empirical realities of PCG. Building from a shared definition of the concept, the constitutive articles analyze an exploratory range of systems, across policy styles, governance levels, and types of actors. Here we consolidate the findings of the articles by identifying five key themes that are drawn from across the special issue, for consideration in future research. These themes are operationalization of PCG systems; voluntary action; temporality; power; and, crucially, effectiveness in mitigating climate change. Our findings provide evidence from a wide range of contexts, from which we build to propose new research streams on this topic.