Recent social science scholarship has sought to understand the visible and invisible impacts of how antibiotics are entrenched as infrastructures and put to work as a proxy for higher levels of care (clinical or otherwise) within modern healthcare. Using a qualitative research design, in this paper our aim is to draw attention to less visible aspects of antimicrobial stewardship (AMS) in residential aged care and their implications for nurse-led optimization of antibiotic use in these settings. By developing an account of the perceptions, experiences and practices of staff regarding the ‘on the ground’ work associated with implementing and upholding AMS objectives our study extends research on attempts to dismantle antibiotic infrastructures in Australian residential aged care facilities (RACF). Drawing on a review of relevant policies, empirical data is presented from fifty-six in-depth interviews conducted in 2021 with staff at 8 different RACFs. Interview participants included managers, nurses, and senior and junior personal care assistants. Our results suggest that registered nurses in residential aged care have been tasked with promoting antibiotic optimization and assigned with AMS responsibilities without sufficient authority and resourcing. A host of hidden care work associated with AMS strategies was evident, reinforcing some staff support for empirical antibiotic prescribing as a ‘safety net’ in uncertain clinical cases. We argue that this hidden work occurs where AMS strategies displace the infrastructural role previously performed by antibiotics, exposing structural gaps and pressures. The inability of organisational accounting systems and the broader AMS policy agenda to capture hidden AMS workflows in RACFs has consequences for future resourcing and organisational learning in ways that mean AMS gaps may remain unaddressed. These results support findings that AMS interventions might not be easily accepted by aged care staff in view of associated burdens which are under recognised and under supported in this domain.