The climate changes we are currently witnessing, accompanied by massive emissions of greenhouse gases on a global scale, are largely anthropogenic in nature, and increasingly reinforce awareness of the need for rapid and timely intervention to contain new carbon emissions into the atmosphere while mitigating their effects. This chapter outlines possible strategies, methodologies, and actions to contribute to the decarbonization of urban districts. Beginning with a detailed review of the literature forming the basis of a structured methodology, a dual field of application has been defined: (1) “green” strategies and actions, through the identification and selection of tree species present in the Mediterranean area with high carbon absorption capacities, and (2) “grey” strategies, actions, and solutions, through the adoption, at various scales, of available technologies and processes for carbon storage (in building envelopes, open space pavements, and underground). These fields of inquiry have been tested in an applied case study (the ERP district of San Basilio, Rome), proposing different intervention scenarios. The contribution aims to define a new original methodological-applicative approach to support the design and meta-design phases in the regeneration of urban districts, aimed at offering concrete responses to contemporary challenges in the field of climate change adaptation and mitigation. Moreover, the research targets designers, architects, and planners and aims to establish a knowledge base and decision-making support through a framework of best practices and actionable measures in the field of construction.