The Korea Middle East respiratory syndrome coronavirus (MERS-CoV) was first confirmed on May 20, 2015, with a subsequent outbreak in South Korea. Five patients with suspected MERS-CoA infection were admitted to our hospital during this outbreak. One patient had no major symptoms upon admission, but pneumonia was identified upon chest radiography. Two patients progressed rapidly to acute respiratory failure and required ventilator-assisted respiration. One patient required extracorporeal membrane oxygenation to treat refractory hypoxemia, and one patient died of shock with multiorgan failure. All the patients had fever, myalgia, leucopenia, normal procalcitonin level, and pneumonia. Importantly, clinicians should test for pneumonia in all suspected patients with MERS-CoV infection, even in the absence of respiratory symptoms. The pneumonia usually affected the lower lobes. A shorter incubation period was associated with more severe disease and greater risk of mortality, and the severity of fever predicted the prognosis of MERS-CoV infection-related pneumonia. Therefore, in cases of lower-lobe pneumonia that occur during an MERS-CoV outbreak and are unesponsive to antibiotics, clinicians should consider the possibility of MERS-CoV infection.