Motivated by the sentiment of the Central Bank of Ireland’s Governor in 2022 that ‘social capital is essential to what central banks do every day and why we do it’, this chapter explores how central banks, driven by their legal mandates and acting within them, can harness forms of ‘soft’ capital to advance their efforts in legitimately addressing climate and nature-related risks. It analyses the legal mandates of central banks in the European Union and the United Kingdom to evidence the foundational argument that climate and sustainability imperatives fit squarely within their mandates to support a protective approach to mitigating climate risk by these central banks. It then explores the concepts of inward-looking ‘organizational cultural capital’ and outward-looking ‘engagement capital’ as manifestations of soft capital that are not only relevant to a protective approach but also to a proactive or legitimate promotional approach by central banks to work coordinatively with governments and other stakeholders to facilitate a net zero transition. In so doing we put forward two novel arguments. First, that central banks must be sustainable and resilient from the inside if they are to meet the challenges presented by climate change imperatives when pursuing their respective mandates. Secondly, that ‘regulator ecosystems for sustainable finance’ are emerging that encourage cooperation and collaboration domestically and also internationally, and help to nudge government leadership of an economy-wide transition.