Humans use punishment to influence each other's behavior. Many current theories presume that this operates as a simple form of incentive. In contrast, we show that people infer the communicative intent behind punishment, which can sometimes diverge sharply from its immediate incentive value. In other words, people respond to punishment not as a reward to be maximized, but as a communicative signal to be interpreted. Specifically, we show that people expect harmless, yet communicative, punishments to be as effective as harmful punishments (Experiment 1). Under some situations, people display a systematic preference for harmless punishments over more canonical, harmful punishments (Experiment 2). People readily seek out and infer the communicative message inherent in a punishment (Experiment 3). And people expect that learning from punishment depends on the ease with which its communicative intent can be inferred (Experiment 4). Taken together, these findings demonstrate that people expect punishment to be constructed and interpreted as a communicative act.