Extant sirenians are the only aquatic herbivorous mammals and comprise four recognized species: the dugong, the Amazonian manatee, the West Indian manatee, and the African manatee. They inhabit coastal shallow waters in tropical and subtropical areas. All sirenian species produce sounds, many of which are audible to humans. These sounds range from tonal and narrowband to pulsed and broadband. Some of these vocalizations can be frequency-modulated and amplitude-modulated, ranging from 0.5 to at least 22 kHz in frequency and from <0.02 to ~1 s in duration. The variation in sound characteristics has enabled call type categorization into barks, chirps, clicks, quacks, squeaks, squeals, trills, whistles, etc., with gradation between classes. These calls are produced in different contexts, such as mother-calf interactions, territorial assertion, and reproductive behaviors. Sirenian vocalizations are also influenced by the surrounding environment, and their communication can be affected by human-produced noise (e.g., motorized vessels). Understanding the function of sirenian sounds in different social and ecological contexts might enhance the application of passive acoustic monitoring to the conservation and management of these endangered animals.