The human tendency to impose costs on those who have behaved antisocially towards third parties (third‐party punishment) has a formative influence on societies, yet very few studies of the development of this tendency exist. In most studies where young children have punished, participants have imposed costs on puppets, leaving open the question as to whether young children punish in real third‐party situations. Here, five‐year‐olds were given the opportunity to allocate desirable or unpleasant items to antisocial and neutral adults, who were presented as real and shown on video. Neutral individuals were almost always allocated only desirable items. Antisocial individuals were instead usually allocated unpleasant items, as long as participants were told they would give anonymously. Most participants who were instead told they would give in person did not allocate unpleasant items, although a minority did so. This indicates that the children interpreted the situation as real, and that whereas they genuinely desired to punish antisocial adults, they did not usually dare do so in person. Boys punished more frequently than girls. The willingness of preschoolers to spontaneously engage in third‐party punishment, occasionally even risking the social costs of antagonizing an anti‐social adult, demonstrates a deep‐seated early‐developing punitive sentiment in humans. Aggr. Behav. 9999:XX–XX, 2014. © 2014 Wiley Periodicals, Inc.