Variation in the acoustic structure of alarm signals has mainly been viewed as coding information about the type of predator or the level of threat posed by the predator. Alarm signals can also convey individuality information, but whether conspecifics use this information and the function of individually distinct alarm calls remains unclear. In this study, we examined whether mobbing alarm calls of superb fairy-wrens (Malurus cyaneus) communicated information about sex, individual identity or kinship and whether this information was stable between years. We then examined the discriminative abilities of adults using playback experiments. We first used a habituation/dishabituation procedure to investigate whether adults were able to differentiate between two unfamiliar individuals. Then, we tested whether they adjusted their response based on their level of familiarity or kinship with the caller by comparing their response to mobbing alarm calls of their mate, a first order relative from the same population, an unrelated individual from the same population, or a distant bird from a different population. Superb fairy-wren mobbing alarm calls conveyed information about individuality, but not sex or kinship, and vocal individuality varied between years. Adults discriminated between two unfamiliar individuals and responded more strongly to playback of calls from their mate and kin versus individuals from another population. We discussed the conditions for discrimination based on individual characteristics rather than categories of individuals.