Despite growing evidence in the US, little evidence has been available to evaluate whether internationally, hospitals in which nurses care for fewer patients have better outcomes in terms of patient survival and nurse retention. To examine the effects of hospital-wide nurse staffing levels (patient-to-nurse ratios) on patient mortality, failure to rescue (mortality risk for patients with complicated stays) and nurse job dissatisfaction, burnout and nurse-rated quality of care. Cross-sectional analysis combining nurse survey data with discharge abstracts. Nurses (N=3984) and general, orthopaedic, and vascular surgery patients (N=118752) in 30 English acute trusts. Patients and nurses in the quartile of hospitals with the most favourable staffing levels (the lowest patient-to-nurse ratios) had consistently better outcomes than those in hospitals with less favourable staffing. Patients in the hospitals with the highest patient to nurse ratios had 26% higher mortality (95% CI: 12-49%); the nurses in those hospitals were approximately twice as likely to be dissatisfied with their jobs, to show high burnout levels, and to report low or deteriorating quality of care on their wards and hospitals. Nurse staffing levels in NHS hospitals appear to have the same impact on patient outcomes and factors influencing nurse retention as have been found in the USA.