Motivated by a growing recognition of the climate emergency, reflected in the 26th Conference of the Parties (COP26), we outline untapped opportunities to improve health through ambitious climate actions in cities. Health is a primary reason for climate action yet is rarely integrated in urban climate plans as a policy goal. This is a missed opportunity to create sustainable alliances across sectors and groups, to engage a broad set of stakeholders, and to develop structural health promotion. In this statement, we first briefly review the literature on health co-benefits of urban climate change strategies and make the case for health-promoting climate action; we then describe barriers to integrating health in climate action. We found that the evidence-base is often insufficiently policy-relevant to be impactful. Research rarely integrates the complexity of real-world systems, including multiple and dynamic impacts of strategies, and consideration of how decision-making processes contend with competing interests and short-term electoral cycles. Due to siloed-thinking and restrictive funding opportunities, research often falls short of the type of evidence that would be most useful for decision-making, and research outputs can be cryptic to decision makers. As a way forward, we urge researchers and stakeholders to engage in co-production and systems thinking approaches. Partnering across sectors and disciplines is urgently needed so pathways to climate change mitigation and adaptation fully embrace their health-promoting potential and engage society towards the huge transformations needed. This commentary is endorsed by the International Society for Environmental Epidemiology (ISEE) and the International Society for Urban Health (ISUH) and accompanies a sister statement oriented towards stakeholders (published on the societies’ websites).