In public goods situations, a specific destructive behaviour reliably emerges when individuals face the possibility of costly punishing others: antisocial punishment, that is, costly punishing cooperative individuals. So far, however, little is known about the individual differences and situational factors that are associated with the dark side of costly punishment. This research deals with this shortcoming. We argue that antisocial punishment reflects the basic characteristics of sadism, namely, aggressive behaviour to dominate and to harm other individuals. We further argue that antisocial punishment may reflect a type of behaviour that allows for the maintenance of self-esteem (through aggressively dominating others). Therefore, we expect that individuals who report a disposition for everyday sadism are particularly likely to engage in antisocial punishment when their self has been threatened (by thinking about one's own death). In a study (N=99), we found empirical support for this assumption. The present research contributes to a better understanding of antisocial punishment and suggests that sadistic tendencies play a crucial role, especially when the self is (existentially) threatened.