Climate change-related health risks are likely to become more prevalent in cities. Cities are also key actors in adaptation to these risks. Adaptation can take place through intentional measures to reduce vulnerability or exposure and unintentionally through other urban policy processes and outcomes. However, complex and dynamic relations between urban policy impacts and vulnerability development are an understudied phenomena. This limits the understanding of how urban climate-related health risks emerge and evolve. We examine urban policy pathways that influence vulnerability to climate-related health impacts with a most similar – most different case study. With a qualitative retrospective analysis of four urban areas in Finland we unveil the mechanism of how urban policy affects urban environment over time and how these impacts and changes shape vulnerability. Contrasting the most different cases, we show that urban policy impacts set differing preconditions to adaptation between local districts. We conclude by suggesting that to adapt to future challenges in cities with respect to social and ecological justice, it is necessary to mainstream adaptation into urban policies with continuous cross-sector and multi-level dialogue about the development of vulnerability.