Life-cycle-based design of constructions is today a crucial aspect of sustainable development. In structural engineering, this means that both the design of new constructions and the retrofitting of existing ones must account for economic, environmental, and social sustainability principles. Although these goals are well defined, there is a lack of design approaches that adopt these principles as key performance criteria. There is therefore a need to develop methodologies that integrate concepts, metrics, and tools aligned with a life-cycle thinking approach. With this aim, the present work proposes an optimization method for the retrofitting of RC buildings using dissipative bracing systems. The method determines the properties of the bracing system by fulfilling safety requirements while optimizing economic and environmental performance, expressed through sustainability-based metrics. This is achieved by assessing structural response on linearized models and evaluating performance using probabilistic approaches such as SAC-FEMA, ensuring the method’s applicability even to complex structures. The paper demonstrates the application of this procedure to an existing multi-storey RC building, presenting and discussing the bracing characteristics, structural response, and life-cycle metric assessment.