While individual distinctiveness in calls seems to be widespread in mammals known as vocal communicants, little is known about animals possessing a small vocal repertoire and relying mostly on visual signals to communicate. Moreover, studies on auditory recognition and social knowledge rarely concerned non-primate species. Horses’ vocal communication for example is poorly known. Here, we first conducted an acoustic analysis of long-distance whinnies in thirty horses, Equus caballus (10 mares, 10 geldings, 10 stallions). We showed that some temporal and more evidently frequency parameters carried reliable information about the caller’s sex, morphology, status and individual identity. Second, we played back to twelve temporarily isolated individuals the whinnies of their group members, known neighbours and stranger horses. Based on vocal cues only, horses adapted their behaviour (e.g. attention vs attraction) to the degree of social familiarity with the caller, while white noise, used as a control, did not elicit any behavioural change. In conclusion, like elephants and hyenas, horses seem to possess a mental representation of their social network and use long-distance calls to decode at least social information but probably also the caller identity.