In urban regeneration projects, balancing environmental, social, and economic aspects is crucial but challenging, often leading to mission drift when team focus deviates from the original goals. Through a case study of regeneration projects at a large U.K. housing association, we explore decision makers’ attention to sustainability, health, and well-being as core elements of social mission. We combined qualitative analysis with an examination of structural complexities and system behaviors, adopting a systems thinking perspective. Analysis of attention patterns in regeneration meetings reveals that attention to the social missions was not sustained, with evident attention shifts toward financial costs and risks. Also, sustainability is prioritized less than health and well-being topics. We use a causal loop diagram to describe the underlying mechanisms that drive attention dynamics, highlighting how the structural complexities can undermine sustainable development in regeneration. Finally, we propose strategies to sustain attention toward sustainability, health, and well-being in regeneration.