Recent reforms in Australian aged care, including the new Aged Care Act, the strengthened Aged Care Quality Standards and the Royal Commission into Aged Care Quality and Safety, call for care that is person‑centred, evidence‑informed, and developed in partnership with those who receive care. While co-design is increasingly promoted to support service reform, there is limited guidance on how this can be achieved with people who live, visit and work in residential aged care homes (RACHs). Here, we describe co-design of the A‑PRECISE model – an infection prevention and control (IPC) strategy - with older people, families and staff in RACHs. Following an initial phase of exploratory interviews, the model evolved through four iterative workshops with residents, family members and the aged care workforce. The workshops included scoping gaps and successes in existing IPC practices, developing and prioritising key messages for everyone in RACHs, reviewing and validating a resource plan, and finally refining a suite of multi-media resources in preparation for pilot testing. The co-design process was cyclical and iterative, enabling shared problem‑solving, negotiation of priorities, and translation of lived experience into practical outputs. Five value‑add opportunities were identified and integrated into the strategy: tailoring education for different audiences; addressing compliance challenges; navigating power imbalances; reinforcing shared responsibility; and embedding interactive approaches to learning. Consistent themes including safety, person-centred messaging, and the importance of the home environment were woven throughout. The A-PRECISE co-design process provides insights into operationalising co-design to support reform, workforce engagement, and sustainable IPC practice in residential aged care.