Climate change, at different scales, is already recognized as an emergency. To achieve the 1.5 °C goal, cities, which in the next years will assist to a further expansion worldwide, are requested to progress toward a climate urbanism. Nature-based solutions (NbS) applied to the built environment, namely, green roofs and walls, and urban greening can contribute to alleviate climate change mitigating urban heat island (UHI), providing a healthier urban environment, and contributing to restore natural ecosystems. In turn, UHI mitigation, a mesoscale phenomenon, has chain effects which can potentially influence upper scales. For instance, UHI mitigation entails a decrease in building energy use for cooling. Furthermore, green roofs and walls can regulate building envelope temperature entailing a potential decrease in insulating materials—which usually are carbon dioxide intensive—avoiding manufacture-related greenhouse gas emissions and guaranteeing, anyway, a comfortable indoor climate. Altogether, NbS can simultaneously result beneficial for both local and global scale. The current chapter investigates, in a geographical multi-scale perspective, benefits, co-benefits, and trade-offs of NbS applied to the built environment, as well as it looks at experiences and approaches used by municipalities to mitigate UHI by means of NbS.