Background: With the advancement of diagnostic methods, a viral infection is increasingly recognized in adult patients with pneumonia and the outcomes can be fatal especially in high-risk patients. We aimed to examine the clinical characteristics of adults with viral pneumonia and also to determine the associated factors with short-term mortality in those patients. Methods: Adult patients who were diagnosed as viral pneumonia between January 2010 and December 2015 were consecutively included. Data were collected through reviews of electronic medical records. The primary outcome was 30-day mortality. Results: A total of 1503 patients with viral pneumonia were included with a mean age of 66.0 years and male predominance in 60%. The most common viral pathogen was rhinovirus, followed by influenza virus and parainfluenza virus (PIV). Viral-bacterial co-infection and multiple viral infections were found in 24.5% and 5.2%, respectively. The 30-day mortality was 7.1% in total patients and it was not different according to viral pathogens. However, cancer patients had higher mortality than non-cancer patients for the PIV (12.3% vs. 3.8%, p < .05) and coronavirus (24.4% vs. 3.0%, p < .01) infections. On the multivariate analysis, old age (>/=65) (OR 1.66, 95% CI: 1.06-2.60), viral-bacterial co-infection (OR 1.61, 95% CI: 1.05-2.48), malignancy (OR 2.26, 95% CI: 1.50-3.40), and shock at the initial presentation (OR 2.12, 95% CI: 1.03-4.37) were significantly associated with mortality. Conclusions: The mortality from viral pneumonia was high in adult patients. Old age, viral-bacterial co-infection, underlying malignancy, and initial shock were independent predictors of mortality.