Background: Using different scores to predict the outcome of patients and determine the severity of their illness could be effective in making better clinical decisions and helping patients. The purpose of this study is to determine the predictive value of the National Early Warning Score (NEWS) and Modified Early Warning Score (MEWS) of in-hospital mortality in patients with a suicide attempt. Methods: In a diagnostic study, we included 453 patients with suicide attempts in the poisoning unit and Intensive Care Unit (ICU) poisoning unit of Sina Hospital from December 2019 to September 2021. Patients’,vital signs and level of consciousness were recorded and then analyzed by statistical methods. Results: The Mean±, SD of patients’,age was 31. 82±, 12. 28 and the mortality rate was 7. 7%. The median (25%-75%) of NEWS and MEWS in all patients was 4(2-7) and 2(1-3), respectively. Based on the Receiver Operating Characteristic (ROC) curve of NEWS, the Area Under The Curve (AUC) (CI95%), standard error, and cut off point were 0. 915(0. 876-0. 995), 0. 020, and 7. 5 respectively (85% sensitivity and 81% specificity) (P˂, 0. 001). The results of MEWS based on Receiver Operating Characteristic (ROC) curve were 0. 87 (0. 805-0. 932), 0. 033, and 3. 5 respectively (74% sensitivity and 84% specificity) (P˂, 0. 001). Conclusion: Based on our study results, we concluded that in hospitalized patients with suicide attempts, the accuracy of NEWS in predicting hospital mortality is higher than MEWS.