People's expectations of acceptance often come to create the acceptance or rejection they anticipate. The authors tested the hypothesis that interpersonal warmth is the behavioral key to this acceptance prophecy: If people expect acceptance, they will behave warmly, which in turn will lead other people to accept them; if they expect rejection, they will behave coldly, which will lead to less acceptance. A correlational study and an experiment supported this model. Study 1 confirmed that participants' warm and friendly behavior was a robust mediator of the acceptance prophecy compared to four plausible alternative explanations. Study 2 demonstrated that situational cues that reduced the risk of rejection also increased socially pessimistic participants' warmth and thus improved their social outcomes.