ObjectiveThis study aimed to assess the economic efficiency of the acute medical unit (AMU) hospitalist care model, utilising patient outcomes (length of hospital stay, emergency department (ED)-length of hospital stay, in-hospital mortality) from a previous investigation.DesignA retrospective cohort study was conducted using benefit–cost analysis from a societal perspective. Data relating to clinical factors, outcomes and medical costs were obtained from the electronic medical record database at our institution. Literature-based costing was applied to determine direct non-medical costs and indirect costs that could not be obtained directly.SettingA tertiary care hospital in the Republic of Korea.ParticipantsWe evaluated 6391 medical inpatients admitted through the ED from 1 June 2016 to 31 May 2017.InterventionsThe study compared multiple types of costs and benefits among inpatients from the ED between a non-hospitalist group and an AMU hospitalist group.ResultsThis investigation found a significant reduction in medical costs and total costs in the AMU hospitalist group compared to the non-hospitalist group (30% reduction, 95% CI: 27.6–32.1%,P=0.000; 29.3% reduction, 95% CI: 27.0–31.5%,P=0.000; respectively). Furthermore, significant reductions in direct and indirect costs were found in the AMU hospitalist group compared to the non-hospitalist group (28.6% reduction, 95% CI: 26.6–30.5%,P=0.000; 23.3% reduction, 95% CI: 20.9–25.5%,P=0.000; respectively). The net-benefit and benefit-cost ratio (BCR) of the AMU hospitalist care group were US $6846 and 1.33 per patient admission, respectively.ConclusionsThe AMU hospitalist care model was associated with remarkable reductions in multiple costs. The results of the sensitivity analysis indicated that the net-benefit estimates of AMU hospitalist care were similar to the baseline estimates. Thus, the overall net-benefit of AMU hospitalist care was found to be largely positive.