We investigated the clinical characteristics of patients with pneumonia caused by Aeromonas species. Patients with pneumonia caused by Aeromonas species during the period 2004 to 2011 were identified from a computerized database of a regional hospital in southern Taiwan. The medical records of these patients were retrospectively reviewed. Of the 84 patients with pneumonia due to Aeromonas species, possible Aeromonas pneumonia was diagnosed in 58 patients, probable Aeromonas pneumonia was diagnosed in 18 patients, and pneumonia due to Aeromonas was conclusively diagnosed in 8 patients. Most of the cases of Aeromonas pneumonia developed in men and in patients of advanced age. A. hydrophila (n = 50, 59.5 %) was the most common pathogen, followed by A. caviae (n = 24, 28.6 %), A. veronii biovar sobria (n = 7, 8.3 %), and A. veronii biovar veronii (n = 3, 3.6 %). Cancer (n = 37, 44.0 %) was the most common underlying disease, followed by diabetes mellitus (n = 27, 32.1 %). Drowning-associated pneumonia developed in 6 (7.1 %) patients. Of 47 patients who were admitted to the intensive care ward, 42 patients developed acute respiratory failure and 24 of those patients died. The overall in-hospital mortality rate was significantly associated with liver cirrhosis, cancer, initial presentation of shock, and usage of mechanical ventilation. In conclusion, Aeromonas species should be considered as one of the causative pathogens of severe pneumonia, especially in immunocompromised patients, and should be recognized as a cause of drowning-associated pneumonia. Cirrhosis, cancer, and shock as the initial presenting symptom are associated with poor outcome.