Introduction: Upper gastrointestinal bleeding (UGIB) is one of the potentially life-threatening gastrointestinal emergencies presenting to the emergency departments (ED) around the globe. Early risk stratification using clinical prediction scores allows appropriate treatment that may help in reducing morbidity and mortality. This study evaluated the efficacy of the addition of red cell distribution width (RDW) to the AIMS65 score for risk stratification of patients presenting to the ED with UGIB. Methods: This prospective observational study over a period of one and a half years recruited 371 patients through consecutive sampling. Data collected included the patients’ vitals, laboratory parameters and interventions like the need for blood transfusion, endoscopic and surgical interventions, invasive ventilation, and re-bleeding after endoscopy. The patients were admitted and managed according to hospital protocols and were followed up for a month for determining the 30-day mortality. Results: Three hundred and forty-eight cases of UGIB were included in this study out of which 56 (16.1%) expired within a span of thirty days. In patients with UGIB, a high RDW (≥15.5%) was strongly associated with 30-day mortality. AUROC of AIMS65 score was found to be 0.936 which marginally increased to 0.939 with the addition of RDW. Conclusion: In UGIB patients, a high RDW (> 15.5%) is strongly associated with 30-day mortality. The combination of RDW with the AIMS65 score marginally increases the discriminatory power of risk stratification in patients presenting to the ED with symptoms of UGIB.