Urban metabolism (UM) is the sum of processes for which cities mobilize, consume, and transform their resources for built environments to function effectively. It consists of interrelated processes working at various urban levels forming an intri-cate socio-environmental network to achieve urban sustainability, including adap-tive reuse of heritage buildings. As significant components of historic urban areas, heritage buildings are adapted for appropriate functions to prolong their lifespans. This standard practice is an ideal solution for reducing adverse environmental impacts of the construction industry given that new buildings consume energy and resources and have large carbon footprints. Moreover, the adaptive reuse of heritage build-ings increases socio-cultural viability and promotes eco-friendly environments. This practice of rehabilitation and reuse has been studied vastly. However, the relation-ship between urban metabolism and heritage buildings from an ecological perspec-tive has not largely gained scholarly attention. Hence, this chapter explores this relationship by advocating that reuse and conservation are ecological principles, and that adopting existing infrastructure such as historical buildings and increasing their life cycles contributes toward desirable urban metabolism. This brings down cost and time of construction, requires less resources, retains a set of materials for longer periods for metabolic processes, and promotes environmental and social sustainability. The chapter reviews relevant literature and specific adaptive reuse case studies in urban areas around the globe including restoration and redevelopment of singular or multiple heritage buildings that display significant positive environmental impacts such as addressing resource depletion and reducing greenhouse gas (GHG) emissions. The chapter also highlights the ecological aspect of a built environment concerning sustainable supply of materials and energy required for a desired urban metabolism. Based on this, the research builds a case for conservation and adap-tive reuse to be employed as an important indicator for urban metabolism through maintenance and management of historical urban built environments.