Objective: In this study, we aimed to explore the role of the plasma presepsin level in patients with community-acquired pneumonia during admission to the emergency department in assessing the diagnosis, severity, and prognosis of the disease. In addition, we wanted to investigate the relationship of presepsinin with procalcitonin, C-reactive protein and pneumonia severity scores. Methods: One hundred twenty-three patients over the age of 18 who presented with a diagnosis of pneumonia to the emergency department were included in the study. The vital signs, symptoms, examination findings, background information, laboratory results, and radiological imaging results of the patients were recorded. The 30-day mortality rates of the patients were determined. Results: A statistically significant difference was found between the presepsin levels of the patients diagnosed with pneumonia and those of healthy subjects (p < 0.05). The plasma presepsin levels of the patients who died (8.63 +/- 6.46) were significantly higher than those of the patients who lived (5.82 +/- 5.97) (p < 0.05). The plasma procalcitonin and C-reactive protein levels of the dead patients were significantly higher than those living (p < 0.05). A presepsin cut-off value of 3.3 ng/mL for 30-day mortality was established (AUROC, 0.65; specificity, 45%; sensitivity, 82%). Procalcitonin is the most successful biomarker in the determination of mortality (AUROC, 0.70). A significant correlation was available between presepsin and lactate, C-reactive protein and procalcitonin (p < 0.05). There was a significant correlation between the Pneumonia Severity Index values and presepsin levels (p < 0.001, r = 0.311). Conclusion: The plasma presepsin level can be utilized for diagnosing community-acquired pneumonia. Plasma presepsin, procalcitonin and C-reactive protein levels can be used to predict the severity and mortality of community-acquired pneumonia.