BackgroundEarly recognition and response to clinical deterioration reduce the frequency of in-hospital cardiac arrests, mortality, and unplanned intensive care unit (ICU) admissions. This study aimed to investigate the impact of the Prioritising Responses Of Nurses To deteriorating patient Observations (PRONTO) intervention on hospital costs and patient length of stay (LOS). MethodThe PRONTO cluster randomised control trial was conducted to improve nurses’ responses to patients with abnormal vital signs. Hospital data were collected pre-intervention (T0) at 6 months (T1) and 12 months (T2) post-intervention. The economic evaluation involved a cost-consequence analysis from the hospital’s perspective. Generalised estimating equations were used to estimate the parameters for regression models of the difference in costs and LOS between study groups and time points. ResultsHospital admission data for 6065 patients (intervention group, 3102; control group, 2963) were collected from four hospitals for T0, T1 and T2. The intervention cost was 69.61 A$ per admitted patient, including the additional intervention training for nurses and associated labour costs. The results showed cost savings and a shorter LOS in the intervention group between T0 − T1 and T0 − T2 (cost differences T0 − T1: −364 (95% CI −3,782; 3049) A$ and T0 − T2: −1,710 (95% CI −5,162; 1,742) A$; and LOS differences T0 − T1: −1.10 (95% CI −2.44; 0.24) days and T0 & T2: −2.18 (95% CI −3.53; −0.82) days). ConclusionThe results of the economic analysis demonstrated that the PRONTO intervention improved nurses’ responses to patients with abnormal vital signs and significantly reduced hospital LOS by two days at 12 months in the intervention group compared to baseline. From the hospital’s perspective, savings from reduced hospitalisations offset the costs of implementing PRONTO.