Legionnaires’ disease is a severe form of pneumonia caused by Legionella species which are ubiquitous in both natural and man-made environments. It causes high morbidity and case fatality rates. The disease is acquired by aspiration of water or inhalation of aerosols containing the bacteria from environmental sources. Early diagnosis and appropriate treatment are important factors in determining the prognosis. Clinical and laboratory predictors will not reliably identify cases of Legionnaires’ disease; therefore, the diagnosis requires specific laboratory tests. Legionnaires’ disease is diagnosed by culture, Legionella urinary antigenuria, polymerase chain reaction, or serologic analyses. Isolation of Legionella from clinical samples is the gold standard. Legionella urinary antigen tests are easy and useful for early diagnosis of Legionnaires’ disease. Fluoroquinolones, macrolides, and doxycycline are drugs of choice. Legionnaires’ disease is considered to be preventable illness since it is possible to control and remove the bacteria in reservoirs. In Turkey, travel-associated Legionnaires’ disease has a specific surveillance program since 1996. After the year of 2015, it became mandatory to take annual water cultures for Legionella from hospital water systems. The aim of this review is to raise awareness of legionellosis and to summarize the current literature.