BACKGROUND: Patients with uncontrolled blood loss often require immediate blood transfusion after the bleeding is stopped. If it is an emergency situation, blood that has not been tested for compatibility (uncrossmatched red blood cell [URBC] products) can be used. However, no studies have been conducted to evaluate the effectiveness of this protocol. AIM: The aim of the study is to evaluate the effectiveness of URBC transfusion in Srinagarind Hospital’s emergency department (ED). METHODS: This was a cross-sectional study that reviewed the medical records of ninty Thai patients over 18 years of age who received at least one unit of blood through URBC transfusion in the Srinagarind Hospital ED from September 2016 to August 2018. RESULTS: The average age of the patients was 47.23 ± 18.2 years, and 73.3% were male. A total of 149 units of URBC were provided, with 54.44% of recipients being trauma patients and 27.78% being gastrointestinal bleeding patients. The 24-h and in-hospital mortality rates were 58.89 and 72.22%, respectively. There were no cases of acute blood transfusion complications or inappropriate URBC transfusion. CONCLUSIONS: The transfusion of URBC necessary in patients with uncontrolled bleeding. No complications were found due to acute blood transfusion.