Background: Early and effective treatment of patients with sepsis requires early recognition in emergency department and understanding the severity of the disease. Many studies have been conducted for this purpose, and many of scoring systems have been developed that provide early recognition of these patients and show their severity. Objectives: The aim of this study is to evaluate the efficacy of the scoring systems used to determine the mortality of patients with infections admitted in emergency department. Methods: In all, 400 patients who admitted to Uludağ University Hospital Emergency Department were prospectively included in this study. In addition to Systemic Inflammatory Response Syndrome score, Quick SOFA score, Mortality in Emergency Department Sepsis score, Modified Early Warning Score, and Charlson Comorbidity Index score in all patients, CURB-65 score was calculated in the patients diagnosed with pneumonia. It has been aimed to determine the power of these scores’ predictive mortality rates and their superiority to each other. Results: It was found that Mortality in Emergency Department Sepsis score and Quick SOFA score could be used with similar efficacy (respectively p = 0.761 and p = 0.073) in determining early mortality in emergency department (5th and 14th days) and that MEDS score was more effective (p < 0.001) in predicting the 28th-day mortality. While these recommendations were valid in patients diagnosed with pneumonia, it was determined that CURB-65 score could also be used to estimate 5th-, 14th-, and 28th-day mortalities (respectively, for the 5th day, p = 0.894 and p = 0.256; for the 14th day, p = 0.425 and p = 0.098; and for the 28th day, p = 0.095 and p = 0.158). The power of Systemic Inflammatory Response Syndrome score, previously used to identify sepsis, in predicting mortality was detected to be lower. Conclusion: Mortality in Emergency Department Sepsis score and Quick SOFA score could be used with similar efficacy in determining early mortality in emergency department. However, if you want to predict 28th-day mortality rate, it can be better to use Mortality in Emergency Department Sepsis score or CURB-65 (in patients diagnosed with pneumonia).