There is a wealth of evidence that demonstrates a link between inadequate nurse staffing levels and suboptimal patient care. Over the last decade, policies and legislation on safe nurse staffing levels have been developed for specific settings and countries in the UK, all of which emphasise employers’ responsibility in responding to staff’s concerns about unsafe staffing. However, the effectiveness of mechanisms for monitoring and responding to such concerns is unclear. This article provides an overview of some of the results of a union-led pilot survey of acute hospital staff that aimed to explore the prevalence of unsafe staffing levels and employers’ responses to concerns raised by staff about staffing levels. Overall, the results demonstrate that hospital staff working in clinical roles often regarded staffing levels as unsafe and that the delivery of nursing interventions was often disrupted on shifts reported as unsafe. In addition, most staff who had raised concerns about staffing levels perceived their employer’s response as unsatisfactory. Employers appeared to rely on staff redeployment or temporary staff to address staffing shortfalls, but these are not always effective or viable options. Employers need to explore alternative means of alleviating staffing shortfalls and of supporting their staff.