WHAT IS KNOWN ON THE SUBJECT?: Literature on staffing levels and outcomes in psychiatric wards is limited and shows mixed associations Lack of economic evidence on conflicts and containment in psychiatric care Data from the City-128 study showed that regular qualified nurse staffing levels in the preceding shifts were associated with raised conflict and containment levels WHAT THIS PAPER ADDS TO EXISTING KNOWLEDGE?: This is the first economic analysis using the City-128 data, with costs and outcomes data have been combined. Cost-effectiveness of different staffing levels in relation to conflicts and containments in England, using data from the City-128 study Both day and night shifts appeared to show that the low staff scenario was cost-effective in terms of conflicts and containment averted, even after attempts were made to adjust for patient severity WHAT ARE THE IMPLICATIONS FOR PRACTICE?: This paper could be an indication towards further investigation into how mental health inpatient care, specially nursing is organized in England. Abstract Introduction Evidence from City-128 study shows a positive association between staffing levels and conflicts/containment. Economic evidence on this topic is scarce, with no economic analyses combining costs and outcomes. Aim/Question To assess the cost-effectiveness of different staffing levels in relation to conflicts and containments in England, using City-128 study data. Methods Shifts were grouped into three groups based on staff-to-bed ratio. Cost information was combined with total conflicts and containment measures to assess cost-effectiveness. Results The cost-effectiveness analysis of the three staffing scenarios for both day and night shifts appeared to show that the low staff scenario was cost-effective in terms of conflicts and containment averted, even adjusting for patient severity. A production function analysis also revealed that increased staff numbers were associated with higher numbers of events. Discussion Causation cannot be attributed and neither can recommendations be made on optimal staffing levels. The impact on other outcomes such as symptoms, functioning and length of stay, and other factors should be explored, and these may all benefit from increased staff numbers. Implications for practice These results indicate that increasing staff numbers may not necessarily improve conflict and containment outcomes. They may produce positive outcomes in other domains.