Amidst a global nursing shortage, ensuring sufficient nurses are available to care for patients is an international policy priority. High-income countries have developed and implemented numerous models to ensure safe nurse staffing, yet evidence to recommend any single methodology remains limited. Existing research primarily evaluates nurse staffing systems by inputs and outcomes, neglecting their internal dynamics. Using qualitative case study data from England and Wales and drawing on practice perspectives and Actor Network Theory, this paper examines these socio-material relations. Healthcare systems are complex, diverse and constantly evolving. Whilst identifying a single 'best' model may prove both impractical and elusive, this paper demonstrates the value of this theoretical approach for understanding the interplay of system components and the mediating effects of context. These insights can inform future research and help improve systems to meet the demands of late modernity.