Objective Data on long-term rebleeding risk and mortality in acute upper gastrointestinal bleeding (AUGIB) patients are scarce and comparison to controls are lacking. Aimsof the study were to assess long-term prognosis of AUGIB patients and compare to controls. Methods A population-based retrospective case-control study conducted at the National University Hospital of Iceland and included all patients who underwent endoscopy in 2010-2011. AUGIB was defined as haematemesis or coffee ground vomiting leading to hospitalization or occurring in a hospitalized patient. Controls underwent endoscopy in 2010-2011, matched for sex/age. Rebleeding was defined as AUGIB >14 days up to five years after index bleeding. Results Overall, 303 patients had AUGIB, mean age 67 (+/- 18), controls66 years (+/- 19), females, 51 and 46%, respectively. The five-year rebleeding rate for AUGIB patients was 13% (95%CI 9-17%), higher than the rate of bleeding events in controls, 3% (95%CI 1-5%; log-rank <0.001), hazard ratio (HR) 6.0 (95%CI 2.4-15) when correcting for comorbidities, NSAID's, PPI's and antithrombotics. The mortality of AUGIB patients at end of follow-up was higher when compared to controls, 39% (95%CI 49-33%) vs. 26% (95%CI 30-21%), log-rank <0.001, comorbidity-adjusted HR 1.4 (1.1-1.9). A subanalysis of non-variceal AUGIB yielded similar results in regard to rebleeding and mortality rates. Conclusions AUGIB patients were at 6-fold risk of rebleeding compared to bleeding events in controls at five years of follow-up. Five-year mortality was higher in AUGIB patients when compared to controls even when correcting for age and comorbidities, suggesting that an episode of AUGIB indicates serious frailty.