The repurposing of manufacturing facilities has provided a solution to the surge in demand for healthcare products during the COVID-19 pandemic. Despite being a widespread and important phenomenon, manufacturing repurposing has received scarce research. This paper develops a grounded understanding of the key factors that influence manufacturing repurposing at the macro and micro levels. We collected rich qualitative data from 45 case studies of firms’ repurposing initiatives during COVID-19. Our study focuses on four types of healthcare products that experienced skyrocketing demand during the first months of the COVID-19 pandemic: face shields, facemasks, hand sanitizers, and medical ventilators. Based on the case studies, we identify and generalize driving factors for manufacturing repurposing and their relationships, which are summarized in causal loop diagrams at both macro and micro levels. Our research provides practitioners, policymakers, and scholars with a conceptual understanding of the phenomenon of manufacturing repurposing. It helps manufacturing managers understand why, when, and how they should engage in manufacturing repurposing and informs policymakers when and how to tailor incentive policies and support schemes to changing situations. Scholars can build on our work to develop and test dynamic system–behavior models of the phenomenon or to pursue other research paths we discover. The world stands to benefit from improved manufacturing repurposing capabilities to be better prepared for future disruptions.