Case studies from global cities contribute to more focused analyses of global warming challenges and demonstrate the performance and effectiveness of mitigation and adaptation strategies to identify lessons about success at the city scale. The case studies were chosen to demonstrate aspects of the critical messages for action priorities in global warming mitigation and adaptation. This work focuses on best practices and initiatives for mitigation and adaptation approaches from developed and developing economies, including North American cities, European cities, Asian cities, and other global cities worldwide. The case studies were grouped to examine, identify, and emphasize important factors in various areas (e.g., local programs and alliances, governance, stakeholder engagement, community actions, and scientific research) that determined the success of adaptation strategies in various global cities. Many recent studies showcase mitigation approaches, particularly those relating to blue-green infrastructure and nature-based strategies. The case studies selected reflect vulnerable regions and demonstrate how increasing global warming significantly concerns individuals, societies, and their infrastructure. The selected studies include Amsterdam in Netherlands; Singapore, as a city in a garden; Boston in USA; Ahmedabad Heat Action Plan in India, aimed at implementing strategies with the objectives of climate adaptation planning; Copenhagen, as a coastal town, is more susceptible to flooding; Portland, the most progressive city in USA; Hamburg in Germany, one of the biggest harbours in Europe; and the 'Rain City Strategy', in Vancouver, Canada. Not all global cities respond the same way, but undertaking joint complex efforts helps mitigate the impacts.