Researchers have debated whether a person’s behavior can be predicted from his or her face. In particular, it is unclear whether people’s trustworthiness can be predicted from their facial appearance. In the present study, we implemented conceptual and methodological advances in this area of inquiry, taking a new approach to capturing trustworthy behavior and measuring targets’ own self-expectations as a mediator between consensual appearance-based judgments and the trustworthiness of targets’ behavior. Using this novel paradigm to capture 900 observations of targets’ behavior (as trustworthy or untrustworthy), we found that face-based judgments predicted trustworthiness. We also found that this effect was mediated by targets’ expectations of how other people would perceive them and by their intentions to act in accordance with those expectations. These results are consistent with an internalized-impressions account: Targets internalize other people’s appearance-based expectations and act in accordance with them, which leads facial-appearance-based judgments to be accurate.