The Kunming–Montreal Global Biodiversity Framework (KM-GBF) provides a major impetus for the restoration and conservation of blue carbon ecosystems to address the biodiversity and climate crises. In this Perspective, we translate the KM-GBF targets for blue carbon ecosystems into quantitative metrics, outline action that must be taken to achieve these goals and quantify the associated climate benefits. To achieve the KM-GBF targets, net mangrove, saltmarsh and seagrass losses of 187–190 km2, 76–126 km2 and 3,068–3,597 km2, respectively, must be avoided annually from 2030 onwards and 23,693–24,369 km2, 10,467–17,296 km2and 90,601–106,215 km2 of these ecosystems must be restored. Achieving the KM-GBF targets would contribute 2.8% of the reduction of carbon emissions needed to limit anthropogenic warming to 2 °C by 2030. However, the cost of achieving the targets (US$520.1 billion yr–1) far exceeds the amount pledged ($200 billion yr–1) for all ecosystems. Thus, research is needed to develop cost-effective restoration and conservation technologies, along with innovative financial models to incentivize investments in nature. Additionally, blue carbon actions must be embedded within National Biodiversity Strategies and Action Plans to ensure that the targets are met.