Purpose Although the diagnostic performance of the bedside lung ultrasound emergency (BLUE) protocol has been well-studied in patients with undifferentiated dyspnea, the data on performance of the BLUE protocol and associated ultrasound artifacts for the diagnosis of pneumonia are limited. This study aimed to determine the performance of the BLUE protocol and each of the BLUE protocol profiles in the diagnosis of pneumonia in the emergency department (ED). Methods Patients admitted to the ED with the symptoms suggesting pneumonia were included. The BLUE protocol was performed by an operator who was blinded to clinical information. Primary outcome was the diagnostic performance of the BLUE protocol for pneumonia. Secondary outcome was the diagnostic contribution of each BLUE protocol profile supporting pneumonia. Results Of the 154 patients included in the study, 112 (72.7%) were diagnosed with pneumonia. The BLUE protocol was able to detect pneumonia in 97 (86.6%) patients with a sensitivity of 86.6%, specificity of 71.4%, and LR+ of 3.03. Among the BLUE protocol profiles, the A/B profile had the highest diagnostic performance with a sensitivity, specificity and LR+ of 48.2, 97.6, and 20.3, respectively. Conclusion The BLUE protocol had a good diagnostic performance for pneumonia. Among the BLUE protocol profiles, the A/B profile had the highest performance for confirming pneumonia in the ED.