Introduction: Aged care clinicians often make complex decisions in busy, resource-limited settings, with limited immediate guidance—especially in the community, where isolation from colleagues is common. Decision support tools (DSTs) can help translate evidence into practical, workflow-friendly guidance. However, most DSTs are not well-suited to aged care challenges. Indwelling urethral catheter insertion is a recognised high-risk procedure associated with preventable adverse events, making it a priority area for a DST. Methods: A co-design and implementation science approach was undertaken within a large Australian aged care provider. Five structured workshops were conducted with nine Registered Nurses from residential and community care services using a World Café methodology. The first three workshops focused on co-designing DST content with front-line clinicians, while two subsequent workshops focused on identifying implementation barriers, enablers, and potential strategies to effect successful implementation. Additional consultations with metropolitan and regional nurses and clinical experts, refined the DST to ensure contextual relevance and clinical accuracy. Results: The co design process produced a workflow driven DST structured across three phases of care: pre-procedure assessment and preparation, navigating complexity during catheterisation, and post-procedure monitoring and empowerment. Participants emphasised the importance of preparation, adaptive troubleshooting, escalation, and person-centred communication. Six implementation strategies were identified: education, training, modelling, persuading, enabling and environmental restructuring. Conclusion: This study shows how co-design, supported by implementation science, can bridge the evidence–practice gap in aged care by addressing clinical complexity, staff isolation, and resource constraints. The approach offers a scalable model for implementing DSTs for high-risk procedures, with potential to improve safety and person-centred care for older Australians.